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Using print() inside recursive functions in Python3
Question: I am following the book Introduction to Computing Using Python, by Ljubomir
Perkovic, and I am having trouble with one of the examples in recursion
section of the book. The code is as follows:
def pattern(n):
'prints the nth pattern'
if n == 0: # base case
print(0, end=' ')
else: #recursive step: n > 0
pattern(n-1) # print n-1st pattern
print(n, end=' ') # print n
pattern(n-1) # print n-1st pattern
For, say, `pattern(1)`, the output should be `0 1 0`, and it should be
displayed horizontally. When calling the function `pattern(1)`, nothing prints
out, however. But if this is followed by a print statement without arguments,
then the results are displayed.
>>>pattern(1)
>>>print()
0 1 0
If I remove the `end` argument of the `print()` functions inside the recursive
function, I get correct output (albeit it displays it vertically):
>>> pattern(1)
0
1
0
This makes me think that the recursive code itself is correct (plus I
confirmed it was with the source provided by the book's website, and with the
errata sheet). I am not sure, however, why the `print` statement isn't
printing the output as the functions run, if the `end` parameter is included.
Any help would be greatly appreciated.
Answer: The `print` function doesn't always flush the output. You should flush it
explicitly:
import sys
def pattern(n):
'prints the nth pattern'
if n == 0: # base case
print(0, end=' ')
else: #recursive step: n > 0
pattern(n-1) # print n-1st pattern
print(n, end=' ') # print n
pattern(n-1) # print n-1st pattern
sys.stdout.flush()
Note that on python3.3 `print` has a new keyword argument `flush` that you can
use to forcibly flush the output(and thus avoid using `sys.stdout.flush`).
* * *
On a general note I'd decouple the output from the pattern, doing, for
example:
def gen_pattern(n):
if n == 0:
yield 0
else:
for elem in gen_pattern(n-1):
yield elem
yield n
for elem in gen_pattern(n-1):
yield elem
def print_pattern(n):
for elem in gen_pattern(n):
print(elem, end=' ')
sys.stdout.flush()
This makes the code more flexible and reusable, and has the advantage of
calling `flush` only once, or you could also call it once every `x`
elements(actually I believe `print` already does this. It flushes if trying to
write many characters on the screen).
In python3.3 the code could be simplified a little:
def gen_pattern(n):
if n == 0:
yield 0
else:
yield from gen_pattern(n-1)
yield n
yield from gen_pattern(n-1)
|
multiprocess.apply_async How do I wrap *args and **kwargs?
Question: I'm trying to get
[`multiprocess.apply_async`](http://docs.python.org/2/library/multiprocessing.html#multiprocessing.pool.multiprocessing.Pool.apply_async)
to take in both `*args` and `**kwargs`. The docs indicate that this might be
possible with the calling sequence:
apply_async(func[, args[, kwds[, callback]]])
But I can not figure out how to get the calling syntax correct. With the
minimal example:
from multiprocessing import Pool
def f(x, *args, **kwargs):
print x, args, kwargs
args, kw = (), {}
print "# Normal call"
f(0, *args, **kw)
print "# Multicall"
P = Pool()
sol = [P.apply_async(f, (x,), *args, **kw) for x in range(2)]
P.close()
P.join()
for s in sol: s.get()
This works as expected giving the output
# Normal call
0 () {}
# Multicall
0 () {}
1 () {}
When args is not an empty tuple, for example `args = (1,2,3)`, the single call
works, but the multiprocessing solution gives:
# Normal call
0 (1, 2, 3) {}
# Multicall
Traceback (most recent call last):
File "kw.py", line 16, in <module>
sol = [P.apply_async(f, (x,), *args, **kw) for x in range(2)]
TypeError: apply_async() takes at most 5 arguments (6 given)
With the kwargs argument I get, for example `kw = {'cat':'dog'}`
# Normal call
0 () {'cat': 'dog'}
# Multicall
Traceback (most recent call last):
File "kw.py", line 15, in <module>
sol = [P.apply_async(f, (x,), *args, **kw) for x in range(2)]
TypeError: apply_async() got an unexpected keyword argument 'cat'
How do I properly wrap `multiprocess.apply_async`?
Answer: You don't have to use `*` and `**` explicitly. Simply pass the tuple and the
dict and let `apply_async` unpack them:
from multiprocessing import Pool
def f(x, *args, **kwargs):
print x, args, kwargs
args, kw = (1,2,3), {'cat': 'dog'}
print "# Normal call"
f(0, *args, **kw)
print "# Multicall"
P = Pool()
sol = [P.apply_async(f, (x,) + args, kw) for x in range(2)]
P.close()
P.join()
for s in sol: s.get()
Output:
# Normal call
0 (1, 2, 3) {'cat': 'dog'}
# Multicall
0 (1, 2, 3) {'cat': 'dog'}
1 (1, 2, 3) {'cat': 'dog'}
Remember that in python's documentation, if a function accepts `*args` and
`**kwargs` its signature explicitly states that:
the_function(a,b,c,d, *args, **kwargs)
In your case:
apply_async(func[, args[, kwds[, callback]]])
There are no `*` there, hence `args` is **one** argument, which is unpacked
when calling `func` and `kwargs` is **one** argument and processed in the same
way. Also note that it's not possible to have other arguments after
`**kwargs`:
>>> def test(**kwargs, something=True): pass
File "<stdin>", line 1
def test(**kwargs, something=True): pass
^
SyntaxError: invalid syntax
|
iPython giving me a syntax error
Question: I'm running python 2.4 right now and have installed iPython onto my ubuntu
machine. The problem I'm having right now is that it keeps giving me an
ImportError whenever I try to launch it from the terminal.
Right now the symbolic link is located `/usr/local/bin` and the actual file is
inside `/usr/bin/`
Error Message:
File "/usr/local/bin/ipython", line 9
except ImportError as e:
^
SyntaxError: invalid syntax
iPython File...
#!/opt/ttools/bin/python ## YES THIS IS THE CORRECT PATH
"""Terminal-based IPython entry point.
"""
from IPython.frontend.terminal.ipapp import launch_new_instance
try:
launch_new_instance()
except ImportError as e:
if "qt.console.qtconsoleapp" in e.message:
print "Could not start qtconsole. Please install ipython-qtconsole"
elif "html.notebook.notebookapp" in e.message:
print "Could not start notebook. Please install ipython-notebook"
else:
# if there is no clue on the cause -- just re-raise
raise
I've never had an issue like this when I had to set it up on my mac...
Any help would be appreciated. Thanks !!
EDIT :: SOLUTION
Download <http://archive.ipython.org/release/0.10.2/ipython-0.10.2-py2.6.egg>
navigate to downloads folder and run the following command:
`sudo easy_install ipython-0.10.2-py2.6.egg`
Answer: iPython dropped support for python < 2.6 since version 0.11, you'll have to
install 0.10 (or possibly even 0.9) from the archive:
<http://archive.ipython.org/release/>
|
How can i quote escape characters in csv writer in python
Question: I am writing the csv file like this
for a in products:
mylist =[]
for h in headers['product']:
mylist.append(a.get(h))
writer.writerow(mylist)
My my few fields are text fields can conatins any characters like `,` `"` `'`
`\n` or anything else. what is the safest way to write that in csv file. also
file will also have integers and floats
Answer: You should use **QUOTE_ALL** quoting option:
import StringIO
import csv
row = ["AAA \n BBB ,222 \n CCC;DDD \" EEE ' FFF 111"]
output = StringIO.StringIO()
wr = csv.writer(output, quoting=csv.QUOTE_ALL)
wr.writerow( row )
# Test:
contents = output.getvalue()
parsedRow = list(csv.reader([contents]))[0]
if parsedRow == row: print "BINGO!"
|
Python yaml dump confuse
Question: Let's say I have a json file like below, call it `src.json`.
{
"main": {
"contenttype": "Document"
},
"dublin": {
"title": "ダウンロード",
"description": "",
"creators": [
"池田大作"
],
"created": "2012-04-23 10:09:34.642940"
}
}
I wanna dump the `dublin` contents to `dst.yaml` using `yaml` in `python`.
Here is my code:
import json
import yaml
with open('src.json') as f:
data = json.load(f)
dump = {'title': data.get('dublin', {}).get('title', ''),
'description': data.get('dublin', {}).get('description', ''),
'creator': data.get('dublin', {}).get('creators',[''])[0],
'created': data.get('dublin', {}).get('created', '')
}
with open('dst.yaml', 'w') as stream:
yaml.safe_dump(dump, stream, allow_unicode=True )
However, I am not satisfied with the result:
{created: '2010-03-26 09:26:44.002029', creator: 池田大作, description: ' ', title: ダウンロード}
The satisfied one should be :
created: 2010-03-26 09:26:44.002029
creator: 池田大作
description: ''
title: ダウンロード
Then, my questions are:
1. Why `'2010-03-26 09:26:44.002029'` has single quotes while `title` and `creator` not? How to remove single quotes around the date ?
2. Where is the line break? It should have with yaml dumping operation.
Any one help!
Answer: 1. Because it has a space in it.
2. Set `default_flow_style=False` in your call to `yaml.dump()`.
* * *
Also, you don't need to do all of that reconstruction; you could just dump the
existing dublin dict directly:
import json
import yaml
with open('src.json') as f:
data = json.load(f)
with open('dst.yaml', 'w') as stream:
yaml.safe_dump(data.get('dublin', {}), stream, allow_unicode=True,
default_flow_style=False)
|
django reset contenttypes mismatch
Question: Have deleted my database.
Have run SyncDb.
Trying to load from dump ..-python manage.py loaddata dump.json.
Get- "<1062 Duplicate entry '' for key.."
Have run "python manage.py reset contentypes"
But get-
Error: Error: contenttypes couldn't be reset. Possible reasons:
* The database isn't running or isn't configured correctly.
* At least one of the database tables doesn't exist.
* The SQL was invalid.
Hint: Look at the output of 'django-admin.py sqlreset contenttypes'. That's the SQL this command wasn't able to run.
The full error: (1217, 'Cannot delete or update a parent row: a foreign key constraint fails')
Have try to run:
> > > from django.core import management
>>>
>>> management.call_command("flush", verbosity=, interactive=False)
>>>
>>> management.call_command("totally reset", "contenttypes", verbosity=,
interactive=False)
>>>
>>> management.call_command("loaddata", "full_test_data.json", verbosity=)
But get- syntax error.
Have python 2.7. and Django 1.4
Any ideas?
Answer: Try setting `foreign_key_checks` false,
DATABASES = {
'default': {
# ...
'OPTIONS': {
"init_command": "SET foreign_key_checks = 0;",
},
}
}
But you should definitely try to use the dumpdata command with the
[\--natural](https://docs.djangoproject.com/en/dev/ref/django-admin/#django-
admin-option---natural) option to make sure there's no hardcoded content types
in your fixtures.
|
apache server not using proper virtualenv with WSGI setting
Question: I am facing a problem related to django wsgi script. I have been using two
virtualenv for my two application and I have deployed these two application on
my local server with different port. Apache configuration file for first
Appplication looks like:
listen 8081
WSGIPythonPath /home/user/app1:/home/user/virtual-env1/lib/python2.7/site-packages
<VirtualHost mylocalip:8081>
ServerAdmin webmaster@localhost
ServerName www.app1.com
DocumentRoot /home/user/app1
<Directory /home/user/app1/static-root>
Options Indexes
Order Allow,Deny
Allow from all
IndexOptions FancyIndexing
</Directory>
<Directory /home/user/app1>
Options Indexes FollowSymLinks MultiViews
AllowOverride None
Order allow,deny
allow from all
</Directory>
WSGIScriptAlias / /home/user/app1/django.wsgi
WSGIPassAuthorization On
Alias "/static" /home/user/workspace/app1/static_root
</VirtualHost>
and Apache configuration for second application is almost same but instead of
virtual-env1, I am using virtual-env2 and different port. But when I run my
second application on the server I got this error.
**AttributeError at /**
'Settings' object has no attribute 'DB_FILES'
Request Method: GET
Request URL: http://mylocalip:8091/
Django Version: 1.4.3
Exception Type: AttributeError
Exception Value: 'Settings' object has no attribute 'DB_FILES'
Exception Location: /home/user/virtual-env1/lib/python2.7/site-packages/django/utils/functional.py in inner, line 185
Python Executable: /usr/bin/python
Python Version: 2.7.2
Python Path:
['/home/user/virtual-env1/lib/python2.7/site-packages/setuptools-0.6c11-py2.7.egg',
'/home/user/virtual-env1/lib/python2.7/site-packages/pip-1.1-py2.7.egg',
'/home/user/app1',
'/home/user/virtual-env1/lib/python2.7/site-packages',
'/usr/local/lib/python2.7/dist-packages/pip-1.1-py2.7.egg',
'/usr/local/lib/python2.7/dist-packages',
'/usr/lib/python2.7',
'/usr/lib/python2.7/plat-linux2',
'/usr/lib/python2.7/lib-tk',
'/usr/lib/python2.7/lib-old',
'/usr/lib/python2.7/lib-dynload',
'/usr/local/lib/python2.7/dist-packages',
'/usr/lib/python2.7/dist-packages',
'/usr/lib/python2.7/dist-packages/PIL',
'/usr/lib/python2.7/dist-packages/gst-0.10',
'/usr/lib/python2.7/dist-packages/gtk-2.0',
'/usr/lib/pymodules/python2.7',
'/usr/lib/python2.7/dist-packages/ubuntu-sso-client',
'/usr/lib/python2.7/dist-packages/ubuntuone-client',
'/usr/lib/python2.7/dist-packages/ubuntuone-control-panel',
'/usr/lib/python2.7/dist-packages/ubuntuone-couch',
'/usr/lib/python2.7/dist-packages/ubuntuone-installer',
'/usr/lib/python2.7/dist-packages/ubuntuone-storage-protocol',
'/home/user/app2',
'/home']
My django.wsgi file loks like this:
import os, sys
apache_configuration = os.path.dirname (__file__)
project = os.path.dirname (apache_configuration)
workspace = os.path.dirname (project)
sys.path.append ("/home/user/app2")
sys.path.append (workspace)
os.environ ['DJANGO_SETTINGS_MODULE'] = 'app2.settings'
import django.core.handlers.wsgi
application = django.core.handlers.wsgi.WSGIHandler ()
I don't know why my server is looking inside the virtual-env1 instead of
virtual-env2. Please help me as I am new to django and wsgi.
Answer: Here's what helped me in similar situation.
My wsgi file looks like this:
import os
import sys
# activate venv
activate_this = 'full_path_to_activate_this.py'
execfile(activate_this, dict(__file__=activate_this))
# insert project path to sys path
path = 'full_path_to_your_project'
if path not in sys.path:
sys.path.insert(0, path)
import django.core.handlers.wsgi
os.environ['DJANGO_SETTINGS_MODULE'] = 'your_settings'
application = django.core.handlers.wsgi.WSGIHandler()
May be this isn't the best approach, but it worked for me.
I remember that I've googled and found many different solutions, here's some
related links:
* [Setting up Apache and Python WSGI to use VirtualEnv](http://stackoverflow.com/questions/6723494/setting-up-apache-and-python-wsgi-to-use-virtualenv)
* [Setting up django on apache (mod_wsgi, virtualenv)](http://stackoverflow.com/questions/10898216/setting-up-django-on-apache-mod-wsgi-virtualenv)
* [Django Apache wsgi virtualenv import error](http://stackoverflow.com/questions/13753151/django-apache-wsgi-virtualenv-import-error)
Hope that helps.
|
Should unit tests run faster with a gevent patched codebase?
Question: We’re investigating gevent as a drop in performance enhancer for our Flask
API. There is a lot of communication over psycopg2 and Redis in our codebase.
We thought we’d try running the test suite with and without:
import gevent.monkey
gevent.monkey.patch_all()
import psycogreen.gevent
psycogreen.gevent.patch_psycopg()
My understanding is that `patch_all()` makes many blocking calls in the
standard library more efficient on the whole by letting other threads perform
work while waiting for the return call.
Our unit tests take about 160 seconds to run in total and the difference
between gevent patched and non-patched was negligible. Should we be seeing the
power of gevent in our test suite, or does it only reveal itself in a real
life production environment?
More info: Using py.test running pretty regular python-2.7.2 unittest. Gevent
1.0rc2.
Answer: Your understanding is correct, but are you running the tests in parallel?
Perhaps [using nose](http://stackoverflow.com/questions/4710142/can-pythons-
unittest-test-in-parallel-like-nose-can)? My understanding is that gevent wont
really improve the 'straight line speed' of any linear code path, its a
mechanism to enable concurrency in a single process.
|
Python: Create a list of nonmatching values
Question: I've been working on program which searches a folder and finds matching files
names based on a list of vaules from an input list and then copies them to a
folder. The program works but now I want to add one extra layer to it; Get a
list of non matching samples and then output it a CSV file. The code is not
efficient, but it gets the job done though I am aware that it may not be
properly set up to do what I ask.
import os, fnmatch, csv, shutil, operator
#Function created to search through a folder location to for using a specific list of keywords
def locate(pattern, root=os.curdir):
matches = []
for path, dirs, files in os.walk(os.path.abspath(root)):
for filename in fnmatch.filter(files, pattern):
matches.append(os.path.join(path, filename))
return matches
#output file created to store the pathfiles
outfile="G:\output.csv"
output=csv.writer(open(outfile,'w'), delimiter=',',quoting=csv.QUOTE_NONE)
#Opens the file and stores the values in each row
path="G:\GIS\Parsons Stuff\samples.csv"
pathfile=open(path,'rb')
openfile=csv.reader((pathfile), delimiter = ',')
samplelist=[]
samplelist.extend(openfile)
#for loop used to return the list of tuples
for checklist in zip(*samplelist):
print checklist
#an empty list used to store the filepaths of sample locations of interest
files=[]
#for loop to search for sample id's in a folder and copies the filepath
for x in checklist:
LocatedFiles=locate(x, "G:\\GIS\\Parsons Stuff\\boring logs\\boring logs\\")
print LocatedFiles
files.append(LocatedFiles)
# flattens the list called files into a managable list
flattenedpath=reduce(operator.add, files)
#filters out files that match the filter .pdf
filteredpath=[]
filteredpath.append(fnmatch.filter(flattenedpath,"*.pdf*"))
#outputs the file path a .csv file called output
output.writerows(files)
pathfile.close()
#location of where files are going to be copied
dst='C:\\TestFolder\\'
#filters out files that match the filer .pdf
filtered=[]
filtered.append(fnmatch.filter(flattenedpath,"*.pdf*"))
filteredpath=reduce(operator.add,filtered)
#the function set() goes through the list of interest to store a list a unique values.
delete_dup=set(filteredpath)
delete_dup=reduce(operator.add,zip(delete_dup))
#for loop to copy files in the list delete_dup
for x in delete_dup:
shutil.copy(x,dst)
My idea is that since the lists "samplelist" and "files" are the same length:
len(samplelist)
36
len(files)
36
I should be able to pull out the index values of each empty list from "files",
pass it to a list which stores the index value which can be used to pull out
elements from "samplelist".
I've tried using the following links for ideas to do this but have had no
luck:
[In Python, how can I find the index of the first item in a list that is NOT
some value?](http://stackoverflow.com/questions/2748235/in-python-how-can-i-
find-the-index-of-the-first-item-in-a-list-that-is-not-some)
[Finding matching and nonmatching items in
lists](http://stackoverflow.com/questions/8960676/finding-matching-and-
nonmatching-items-in-lists)
[In Python, how do I find the index of an item given a list containing
it?](http://stackoverflow.com/questions/176918/in-python-how-do-i-find-the-
index-of-an-item-given-a-list-containing-it?rq=1)
[Pythonic way to compare two lists and print out the
differences](http://stackoverflow.com/questions/2387981/pythonic-way-to-
compare-two-lists-and-print-out-the-differences?rq=1)
**Following is the output from the list called "samplelist"**
`('*S42TPZ2*', '*S3138*', '*S2415*', '*S2378*', '*S2310*', '*S2299*',
'*S1778*', '*S1777*', '*S1776*', '*S1408*', '*S1340*', '*S1327*', '*RW-61*',
'*MW-247*', '*MW-229*', '*MW-228*', '*MW-209*', '*MW-208*', '*MW-193*',
'*M51TPZ6*', '*M51TP21*', '*H1013*', '*H1001*', '*H0858*', '*H0843*',
'*H0834*', '*H0514*', '*H0451*', '*H0450*', '*EY1TP9*', '*EY1TP7*',
'*EY1TP6*', '*EY1TP5*', '*EY1TP4*', '*EY1TP2*', '*EY1TP1*')`
**Following is the output from the list called "files"**(I am not going to
list all the outputs since it is unnecessary, just wanted to give an idea of
what the list looks like)
`[[], [], ['G:\\GIS\\Parsons Stuff\\boring logs\\boring logs\\S2415.pdf'],
['G:\\GIS\\Parsons Stuff\\boring logs\\boring logs\\S2378.pdf'],
['G:\\GIS\\Parsons Stuff\\boring logs\\boring logs\\MW-247.S2310.pdf',
'G:\\GIS\\Parsons Stuff\\boring logs\\boring logs\\S2310.MW-247.pdf',
'G:\\GIS\\Parsons Stuff\\boring logs\\boring logs\\S2310.pdf'],
['G:\\GIS\\Parsons Stuff\\boring logs\\boring logs\\S2299.pdf'],
['G:\\GIS\\Parsons Stuff\\boring logs\\boring logs\\S1778.pdf'],
['G:\\GIS\\Parsons Stuff\\boring logs\\boring logs\\S1777.pdf'],
['G:\\GIS\\Parsons Stuff\\boring logs\\boring logs\\S1776.pdf'],
['G:\\GIS\\Parsons Stuff\\boring logs\\boring logs\\S1408.pdf']`
Answer: I'm not quite sure this is what you are asking for but couldn't you:
index_list = []
for n, item in enumerate(list):
if len(item) == 0:
index_list.append(n)
that little piece of code will iterate over you list and if the list contain
an empty list it will return the index of the empty list and add it to another
list!
|
How can i check call arguments if they will change with unittest.mock
Question: One of my classes accumulates values in a list, uses the list as an argument
to a method on another object and deletes some of the values in this list.
Something like
element = element_source.get()
self.elements.append(element)
element_destination.send(elements)
self.remove_outdated_elements()
But when when i was trying to test this behavior, i've found that mocks don't
copy their arguments.
>>> from unittest.mock import Mock
>>> m = Mock()
>>> a = [1]
>>> m(a)
<Mock name='mock()' id='139717658759824'>
>>> m.call_args
call([1])
>>> a.pop()
1
>>> m.assert_called_once_with([1])
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python3.3/unittest/mock.py", line 737, in assert_called_once_with
return self.assert_called_with(*args, **kwargs)
File "/usr/lib/python3.3/unittest/mock.py", line 726, in assert_called_with
raise AssertionError(msg)
AssertionError: Expected call: mock([1])
Actual call: mock([])
Is there a way to make Mock copy it's call arguments? If not, what is the best
way to test this kind of behavior?
Answer: There is a chapter "[Coping with mutable
arguments](http://docs.python.org/dev/library/unittest.mock-
examples.html#coping-with-mutable-arguments)" in the documentation, which
suggests several solutions to your problem.
I'd go with this one:
>>> from copy import deepcopy
>>> class CopyingMock(MagicMock):
... def __call__(self, *args, **kwargs):
... args = deepcopy(args)
... kwargs = deepcopy(kwargs)
... return super(CopyingMock, self).__call__(*args, **kwargs)
...
>>> c = CopyingMock(return_value=None)
>>> arg = set()
>>> c(arg)
>>> arg.add(1)
>>> c.assert_called_with(set())
>>> c.assert_called_with(arg)
Traceback (most recent call last):
...
AssertionError: Expected call: mock(set([1]))
Actual call: mock(set([]))
>>> c.foo
<CopyingMock name='mock.foo' id='...'>
|
Issue installing cx_Oracle on Linux - Import only works from Site-Packages Directory
Question: I have installed cx_Oracle to connect Python and Oracle for programming;
however, I can only import cx_Oracle into python if I am in the directory
where cx_Oracle lives. How can I import cx_Oracle globally? Below is code
demonstrating the problem.
Thanks for your help.
**Python Can't Import cx_Oracle**
user@T420 ~ $ python
Python 2.7.3 (default, Sep 26 2012, 21:51:14)
[GCC 4.7.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import cx_Oracle
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: No module named cx_Oracle
**Python Can Import cx_Oracle from the Directory Where it is Located**
user@T420 /usr/lib/python2.7/site-packages $ ls
cx_Oracle-5.1.2-py2.7.egg-info cx_Oracle.so
user@T420 /usr/lib/python2.7/site-packages $ python
Python 2.7.3 (default, Sep 26 2012, 21:51:14)
[GCC 4.7.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import cx_Oracle
>>>
Answer: Python on Debian does not use the site-packages folder. You can simply move
the files into the dist-packages folder and everything should work. The other
solution as Aaron mentioned would be to add the path to site-packages into the
sys.path folder. However, the python site.py folder says the following:
**Quote from site.py file:**
> For Debian and derivatives, this sys.path is augmented with directories for
> packages distributed within the distribution. Local addons go into
> /usr/local/lib/python/dist-packages, Debian addons install into
> /usr/{lib,share}/python/dist-packages. /usr/lib/python/site-packages is not
> used.
|
Python background process not writing to MySQL db
Question: I apologize if this question has been asked before, but I was unable to find
any record of this issue. Full disclosure: I've only been using Python for a
few months and MySQL for about 1 month.
I've written a short Python script on a Raspberry Pi (running Raspbian Wheezy)
that sniffs wifi packets and writes signal strength info to a MySQL database.
I've also created a small PHP file that grabs the info from the database and
presents it in a table (pretty basic). All components of this little system
work exactly as planned, however...
When I run the Python script in the background (sudo python my_script.py &) it
does not appear to update the MySQL database with new readings. Yet it also
throws no errors and outputs to the console without a problem (I have a line
printed each time a wifi packet is intercepted and its RSSI is added to the
database). I encountered the same problem when starting the script at boot up
using the /etc/rc.local file. No errors, but no updates in the database
either.
Is the problem on the Python side of things? A MySQL setting that I need to
change? Is there something else I'm completely missing?
EDITED TO ADD CODE:
#!/usr/bin/python
# -*- coding: utf-8 -*-
import MySQLdb as mdb
import sys
from scapy.all import *
# Create connection to MySQL database called 'DATABASE' at localhost with username 'USERNAME' and password 'PASSWORD'
HOST = "localhost"
USER = "USERNAME"
PW = "PASSWORD"
DB = "DATABASE"
con = mdb.connect(HOST, USER, PW, DB)
# set interface that will be used to monitor wifi
interface = "mon0"
with con:
cur = con.cursor()
# This function will be called every time a packet is intercepted. Packet is passed to function as 'p'
def sniffmgmt(p):
# These are the 3 types of management frames that are sent exclusively by clients (allows us to weed out packets sent by APs)
stamgmtstypes = (0, 2, 4)
if p.haslayer(Dot11):
# Make sure packet is a client-only type
if p.subtype in stamgmtstypes:
# Calculate RSSI
sig_str = -(256-(ord(p.notdecoded[-4:-3])))
# Update database with most recent detection
cur.execute("REPLACE INTO attendance(mac_address, rssi, timestamp) VALUES('%s', %d, NOW())" % (p.addr2, sig_str))
# Print MAC address that was detected (debugging only)
print "MAC Address (%s) has been logged" % (p.addr2)
# Tell scapy what interface to use (see above) and which function to call when a packet is intercepted. lfilter limits packets to management frames.
sniff(iface=interface, prn=sniffmgmt, store=0, lfilter=lambda x:x.type==0)
Thanks! Kyle
P.S. For those who are wondering: this is not intended for malicious use, it
is being used to investigate product tracking techniques at our warehouse.
Answer: I expect you're not calling `commit` on the db transaction.
|
python ctypes vs namedtuple
Question: So I have two simple ctypes struct
class S2 (ctypes.Structure):
_fields_ = [
('A2', ctypes.c_uint16*10),
('B2', ctypes.c_uint32*10),
('C2', ctypes.c_uint32*10) ]
class S1 (ctypes.Structure):
_fields_ = [
('A', ctypes.c_uint16),
('B', ctypes.c_uint32),
('C', S2) ]
Is it possible to do this same for example with namedtuple? How lists are
handled in namedtuple?
Edit:
struc.pack usage
test_data = '0100000002000000' + 10*'01' + 10*'01' + 10*'01'
S2 = collections.namedtuple('S2', ['A2', 'B2', 'C2'])
S1 = collections.namedtuple('S1', ['A', 'B', 'REF_to_S2'])
Data2 = S2._make(struct.unpack('10p10p10p', binascii.unhexlify(test_data[16:])))
##this is not working, because there must be 3 args..
Data1 = S1._make(struct.unpack('ii', binascii.unhexlify(test_data[0:16])))
In the end i want to print data in readable format ( having key:value pairs
visible). But now i cannot figure out how should i handle that unpack
operation with two diffrent namedtuples...?
this unpack.struct operation will take care that value type issues, right ?
Answer: > Is it possible to do this same for example with namedtuple?
It depends on what you mean by "same". You can easily create `namedtuple`
types with the same fields:
S2 = collections.namedtuple('S2', ['A2', 'B2', 'C2'])
S1 = collections.namedtuple('S1', ['A', 'B', 'C'])
However, they're obviously not the same type, and won't have the same
behavior.
* * *
First, these fields are normal Python attributes (and also normal `tuple`
members), which means they don't have static types; they can hold values of
any type.
So, you can do this:
s2 = S2([ctypes.c_uint16(i) for i in range(10)],
[ctypes.c_uint32(i) for i in range(10)],
[ctypes.c_uint32(i) for i in range(10)])
s1 = S1(ctypes.c_uint16(1), ctypes.c_uint32(2), s2)
But you can also do this:
s2 = S2('a', 'b', 'c')
s1 = S1('d', 'e', s2)
… or even:
s1 = S1('d', 'e', 'f')
And also, note that even the first example actually created `list`s of 10
`ctypes` values, not `ctypes` arrays. If you want that, you have to cast them
explicitly.
* * *
Second, `namedtuple`s are an extension of `tuple`s, which means they're
immutable, so you can't do this:
s1.C = s2
* * *
And most importantly, a `namedtuple` can't be used as a `ctypes.Structure`—you
can't pass it to a C function, you have to write manual logic (e.g., around
`struct.pack`) if you want to serialize it in some specific binary format,
etc.
* * *
> How lists are handled in namedtuple?
As mentioned above, the members of a `namedtuple` aren't statically typed, and
can hold values of any type. So, they're handled the same way they are in a
`tuple`, `list`, a normal class instance, a global variable, etc. Just stick a
`list` in there and you've got a `list`.
* * *
> yes that stuct.pack is what i need. But i cannot figure out how i should
> point that the last value in s1 is reference to s2 structure.
From the `namedtuple` side, you just use an `S2` instance as the value for the
`S1.C`, as in my examples above. Again, the items/attributes of a `namedtuple`
are just like any other attributes/variables/etc. in Python, just names that
hold references to objects. So, `s1 = S1(1, 2, s2)` will make the third item
of `s1` into another reference to the same object that `s2` refers to.
As for how to use `struct` to serialize the data: The `struct` module doesn't
have any way to directly delegate to an embedded object. But since the output
of `pack` is just a `bytes` (or, in Python 2.x, `str`) object, you can do this
with normal string manipulation:
# version 1
s2_struct = struct.Struct('!HII')
s1_header = struct.Struct('!HI')
def pack_s2(s2):
return s2_struct.pack(s2.A2, s2.B2, s2.C2)
def unpack_s2(s2):
return S2._make(s2_struct.unpack(s2))
def pack_s1(s1):
return s1_header.pack(s1.A, s1.B) + pack_s2(s1.C)
def unpack_S1(s1):
offset = len(s1_header)
a, b = s1_header.unpack(s1[:offset])
c = unpack_s2(s1[offset:])
return S1._make(a, b, c)
(I personally would use `S2(*struct.unpack` rather than `S2._make`, but since
the documentation does the latter repeatedly, I guess that has to be the
intended way to do things…)
Alternatively, you can flatten the format strings manually:
s2_struct = struct.Struct('!HII')
s1_struct = struct.Struct('!HIHII')
def pack_s2(s2):
return s2_struct.pack(s2.A2, s2.B2, s2.C2)
def pack_s1(s1):
return s1_struct.pack(s1.A, s1.B, s1.C.A2, s1.C.B2, s1.C.C2)
def unpack_s2(s2):
return S2._make(s2_struct.unpack(s2))
def unpack_S1(s1):
a, b, a2, b2, c2 = s1_struct.unpack(s1)
c = S2(a2, b2, c2)
return S1(a, b, c)
I think the second version is easier to read, but it's also easier to get
wrong, and requires you to think about composing objects at the binary level
instead of the Python level, so… choose whichever you find the lesser of two
evils.
|
Two Class instances in Python not different
Question: I'm working on another data acquisition project, which has turned into an
object oriented programming question. In “main” at the bottom of my code I
make two instances of the Object DAQInput. When I wrote this, I thought my
method .getData would refer to the taskHandle of the particular instance, but
it does not. When I run, the code does the getData task with the first handle
twice, so clearly I don’t really understand object oriented programming in
Python. I’m sorry this code will not run without PyDAQmx and a National
Instruments board attached.
from PyDAQmx import *
import numpy
class DAQInput:
# Declare variables passed by reference
taskHandle = TaskHandle()
read = int32()
data = numpy.zeros((10000,),dtype=numpy.float64)
sumi = [0,0,0,0,0,0,0,0,0,0]
def __init__(self, num_data, num_chan, channel, high, low):
""" This is init function that opens the channel"""
#Get the passed variables
self.num_data = num_data
self.channel = channel
self.high = high
self.low = low
self.num_chan = num_chan
# Create a task and configure a channel
DAQmxCreateTask(b"",byref(self.taskHandle))
DAQmxCreateAIThrmcplChan(self.taskHandle, self.channel, b"",
self.low, self.high,
DAQmx_Val_DegC,
DAQmx_Val_J_Type_TC,
DAQmx_Val_BuiltIn, 0, None)
# Start the task
DAQmxStartTask(self.taskHandle)
def getData(self):
""" This function gets the data from the board and calculates the average"""
print(self.taskHandle)
DAQmxReadAnalogF64(self.taskHandle, self.num_data, 10,
DAQmx_Val_GroupByChannel, self.data, 10000,
byref(self.read), None)
# Calculate the average of the values in data (could be several channels)
i = self.read.value
for j in range(self.num_chan):
self.sumi[j] = numpy.sum(self.data[j*i:(j+1)*i])/self.read.value
return self.sumi
def killTask(self):
""" This function kills the tasks"""
# If the task is still alive kill it
if self.taskHandle != 0:
DAQmxStopTask(self.taskHandle)
DAQmxClearTask(self.taskHandle)
if __name__ == '__main__':
myDaq1 = DAQInput(1, 4, b"cDAQ1Mod1/ai0:3", 200.0, 10.0)
myDaq2 = DAQInput(1, 4, b"cDAQ1Mod2/ai0:3", 200.0, 10.0)
result = myDaq1.getData()
print (result[0:4])
result2 = myDaq2.getData()
print (result2[0:4])
myDaq1.killTask()
myDaq2.killTask()
Answer: These variables:
class DAQInput:
# Declare variables passed by reference
taskHandle = TaskHandle()
read = int32()
data = numpy.zeros((10000,),dtype=numpy.float64)
sumi = [0,0,0,0,0,0,0,0,0,0]
Are class variables. They belong to the class itself and are shared among
instances of the class (i.e. if you modify `self.data` in `Instance1`,
`Instace2`'s `self.data` is modified as well).
If you want them to be instance variables, define them in `__init__`.
|
Using Beautiful Soup to extract Norwegian text from HTML files, losing the Norwegian characters
Question: I have a Python script that uses Beautiful Soup to extract the text from HTML
files in a directory. However, I'm having trouble getting the encoding to work
properly. At first I though there may be a problem with the HTML files
themselves. However, when I view the source of an HTML file in Notepad.exe, I
for instance see this: `Vi er her for deg, og du må gjerne ta kontakt med oss
på 815 32 000 eller på Facebook om du har noen spørsmål.`
However, when I view the same HTML file in Internet Explorer, I see this: `Vi
er her for deg, og du må gjerne ta kontakt med oss på 815 32 000 eller på
Facebook om du har noen spørsmål.`
And, the Internet Explorer text is the same text that my Python script appends
into my text file. So, obviously the encoding is detectable, and it's no
surprise that IE doesn't understand it, but I can't seem to figure out why
Python can't handle it. The encoding should be latin-1, which I thought
wouldn't be a problem. Here's the code I have:
import os
import glob
from bs4 import BeautifulSoup
path = "c:\\users\\me\\downloads\\"
for infile in glob.glob(os.path.join(path, "*.html")):
markup = (infile)
soup = BeautifulSoup(open(markup, "r").read())
with open("example.txt", "a") as myfile:
myfile.write(soup.get_text())
myfile.close()
Being as that seems to break the encoding, I thought I could pass latin-1
encoding, like so:
soup = BeautifulSoup(open(markup, "r").read())
soup = soup.prettify("latin-1")
But that gives me the error:
Traceback (most recent call last):
File "bsoup.py", line 12, in <module>
myfile.write(soup.get_text())
AttributeError: 'bytes' object has no attribute 'get_text'
Answer: `.prettify()` already returns bytes, so you just write that directly to the
file, but you have to open that file in _binary_ mode (note the `'ab'` mode
used below):
soup = BeautifulSoup(open(markup, "r").read())
with open("example.txt", "ab") as myfile:
myfile.write(soup.prettify('latin-1'))
There is no need to call `myfile.close()`; the `with` statement already takes
care of that.
To save only the text, open the file in text mode (`'a'`) and specify the
encoding to use on save:
soup = BeautifulSoup(open(markup, "r").read())
with open("example.txt", "a", encoding='latin-1') as myfile:
myfile.write(soup.get_text())
Now Python will automatically encode the unicode text to latin-1 for you.
When you see something like `Ã¥` instead of `å`, then you are interpreting
UTF-8 bytes as Latin-1.
You may want to read up on Python and Unicode:
* [The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets (No Excuses!)](http://joelonsoftware.com/articles/Unicode.html) by Joel Spolsky
* The [Python Unicode HOWTO](http://docs.python.org/3/howto/unicode.html)
* [Pragmatic Unicode](http://nedbatchelder.com/text/unipain.html) by Ned Batchelder
|
PIP install my OS project
Question: I've created an open source project and tried to register it with PIP so
people can use pip install. Unfortunately I can't seem to get it work. Here
are the commands I've tried:
Created a setup.py file:
from distutils.core import setup
setup(name='AyeGotchoPayCheque',
version='.9',
description='Payment Gateway Interface',
author='Rico Cordova',
author_email='[email protected]',
url='http://www.python.org/sigs/ayegotchopaycheque-sig/',
packages=['ayegotchopaycheque', 'ayegotchopaycheque'],
)
Then I used the command `python setup.py register` and answered the questions.
I've tried several other solutions and can't seem to get this working.
Any suggestions?
EDIT 1: It seems I've successfully registered my project with the wrong
`name=AyeGotchoPayChecque`, note the extra "c". How can I "unregister" this
project and re-register with the correct name?
Answer: To "unregister", log into PyPI and go to the account page for the package you
registered, then click on the "Remove this package completely" button. Then,
you can reregister with the correct name. Don't forget to upload the project
as well. I prefer to do it at the same time that I register:
python setup.py egg_info -RDb "" sdist register upload
Each time you upgrade your package's version number, re-run the above code,
and PyPI will keep all versions of your package on the package's website.
|
Python HTTP Error 403 Forbidden
Question: I am a bit of a Python Newbie, and I've just been trying to get some code
working.
Below is the code, and also the nasty error I keep getting.
>
> import pywapi import string
>
> google_result = pywapi.get_weather_from_google('Brisbane')
>
> print google_result
> def getCurrentWather():
> city = google_result['forecast_information']['city'].split(',')[0]
> print "It is " +
> string.lower(google_result['current_conditions']['condition']) + " and
> " + google_result['current_conditions']['temp_c'] + " degree
> centigrade now in "+ city+".\n\n"
> return "It is " +
> string.lower(google_result['current_conditions']['condition']) + " and
> " + google_result['current_conditions']['temp_c'] + " degree
> centigrade now in "+ city
>
> def getDayOfWeek(dayOfWk):
> #dayOfWk = dayOfWk.encode('ascii', 'ignore')
> return dayOfWk.lower()
>
> def getWeatherForecast():
> #need to translate from sun/mon to sunday/monday
> dayName = {'sun': 'Sunday', 'mon': 'Monday', 'tue': 'Tuesday', 'wed':
> 'Wednesday', ' thu': 'Thursday', 'fri': 'Friday', 'sat':
> 'Saturday', 'sun': 'Sunday'}
>
> forcastall = []
> for forecast in google_result['forecasts']:
> dayOfWeek = getDayOfWeek(forecast['day_of_week']);
> print " Highest is " + forecast['high'] + " and "+ "Lowest is " +
> forecast['low'] + " on " + dayName[dayOfWeek]
> forcastall.append(" Highest is " + forecast['high'] + " and "+
> "Lowest is " + forecast['low'] + " on " + dayName[dayOfWeek])
> return forcastall
>
Now is the error:
>
> Traceback (most recent call last): File
> "C:\Users\Alex\Desktop\JAVIS\JAISS-master\first.py", line 5, in
> <module>
> import Weather File "C:\Users\Alex\Desktop\JAVIS\JAISS-
> master\Weather.py", line 4, in
> <module>
> google_result = pywapi.get_weather_from_google('Brisbane') File
> "C:\Python27\lib\site-packages\pywapi.py", line 51, in
> get_weather_from_google
> handler = urllib2.urlopen(url) File "C:\Python27\lib\urllib2.py", line
> 126, in urlopen
> return _opener.open(url, data, timeout) File
> "C:\Python27\lib\urllib2.py", line 400, in open
> response = meth(req, response) File "C:\Python27\lib\urllib2.py", line
> 513, in http_response
> 'http', request, response, code, msg, hdrs) File
> "C:\Python27\lib\urllib2.py", line 438, in error
> return self._call_chain(*args) File "C:\Python27\lib\urllib2.py", line
> 372, in _call_chain
> result = func(*args) File "C:\Python27\lib\urllib2.py", line 521, in
> http_error_default
> raise HTTPError(req.get_full_url(), code, msg, hdrs, fp) HTTPError: HTTP
> Error 403: Forbidden
>
Thanks for any help I can get!
Answer: The 403 error doesn't come from your code but from Google. Google lets you
know that you don't have permission to access the resource you were
requesting, in this case the weather API, because it has been discontinued
(403 technically stands for Forbidden, they could also have gone for 404 Not
Found or 410 Gone).
For more information, read <http://thenextweb.com/google/2012/08/28/did-
google-just-quietly-kill-private-weather-api/>
Other than that, your code is correct.
|
How to use a array of heaps in python
Question: I need to create and use n heaps, I am trying to use heapq and is trying to
push elements into a list of lists, where each element is to be considered a
seperate heap. But its behaving weirdly. I just wanna push the elements 6 and
7 into my 3rd heap. but its getting pushed into all my heaps. any way out of
this??
>>> test
[[], [], [], []]
>>>
>>> heappush(test[2],6)
>>> heappush(test[2],7)
>>> test
[[6, 7], [6, 7], [6, 7], [6, 7]]
Answer: You seem to have created `test` something like this:
>>> from heapq import heappush
>>> test = [[]] * 4
>>>
>>> heappush(test[2],6)
>>> heappush(test[2],7)
>>> test
[[6, 7], [6, 7], [6, 7], [6, 7]]
This creates four references to the _same_ list object. Use a list
comprehension to make four distinct lists:
>>> test = [[] for _ in range(4)]
>>> heappush(test[2],6)
>>> heappush(test[2],7)
>>> test
[[], [], [6, 7], []]
|
Draw a terrain with python?
Question: I have a numpy 2d-array representing the geometrical height of a specific area
where a street will be build. I can visualize this using `scipy.misc.toimage`.
However I would like to get a simple 3D view of the area. Is there a simple
way to plot or render this data as an 3d-image?
Answer: Perhaps use matplotlib's
[plot_surface](http://matplotlib.org/mpl_toolkits/mplot3d/tutorial.html#surface-
plots) or
[plot_wireframe](http://matplotlib.org/mpl_toolkits/mplot3d/tutorial.html#wireframe-
plots):
import matplotlib.pyplot as plt
import numpy as np
import mpl_toolkits.mplot3d.axes3d as axes3d
np.random.seed(1)
fig, ax = plt.subplots(subplot_kw=dict(projection='3d'))
N = 100
X, Y = np.meshgrid(np.arange(N), np.arange(N))
heights = np.sin(2*np.pi*np.sqrt(X**2+Y**2)/N)
ax.plot_surface(X, Y, heights, cmap=plt.get_cmap('jet'))
plt.show()
These functions require three 2D-arrays: X, Y, Z. You have the heights, `Z`.
To generate the standard `X` and `Y` locations associated with those `Z`s, you
could use `np.meshgrid`.
|
How to convert country names to ISO 3166-1 alpha-2 values, using python
Question: I have a list of countries like:
countries=['American Samoa', 'Canada', 'France'...]
I want to convert them like this:
countries=['AS', 'CA', 'FR'...]
Is there any module or any way to convert them?
Answer: There is a module called
[`pycountry`](https://pypi.python.org/pypi/pycountry).
Here's an example code:
import pycountry
input_countries = ['American Samoa', 'Canada', 'France']
countries = {}
for country in pycountry.countries:
countries[country.name] = country.alpha2
codes = [countries.get(country, 'Unknown code') for country in input_countries]
print codes # prints [u'AS', u'CA', u'FR']
|
Dynamically place legend in plot
Question: I am creating plots in pyplot in Python. Each plot contains two or more
subplots. I know I can statically place a legend in the plot by defining the
parameter `loc`; however, my choice of location will sometimes cover the data
in my plot. How would I place the legend dynamically in the location that
interferes with the data the least?
Answer: As tcaswell has already stated, use `ax.legend(loc='best')`:
import matplotlib.pyplot as plt
import numpy as np
pi = np.pi
sin = np.sin
t = np.linspace(0.0, 2 * pi, 50)
markers = ['+', '*', ',', ] + [r'$\lambda$']
phases = [0, 0.5]
fig, ax = plt.subplots(len(phases))
for axnum, phase in enumerate(phases):
for i, marker in enumerate(markers, 1):
ax[axnum].plot(t, i*sin(2*t + phase*pi), marker=marker,
label='$i,\phi = {i},{p}$'.format(i=i, p=phase))
ax[axnum].legend(loc='best', numpoints=1)
plt.show()
Interestingly, the location of the legend is not fixed. If you move the graph
using the GUI, the location of the legend will readjust itself automatically.
|
python package import modules using __init__.py
Question: I have made a package in the following structure:
test.py
pakcage1/
__init__.py
module1.py
module2.py
In the `test.py` file, with the code
from package1 import *
what I want it to do is to
from numpy import *
from module1 import *
from module2 import *
**What should I write in`__init__.py` file to achieve this?**
Currently in my `__init__.py` file I have
from numpy import *
__all__ = ['module1','module2']
and this doesn't give me what I wanted. In this way numpy wan't imported at
all, and the modules are imported as
import module1
rather than
from module1 import *
Answer: If you want this, your `__init__.py` should contain just what you want:
from numpy import *
from module1 import *
from module2 import *
When you do `from package import *`, it imports all names defined in the
package's `__init__.py`.
Note that this could become awkward if there are name clashes among the
modules you import. If you just want convenient access to the functions in
those modules, I would suggest using instead something like:
import numpy as np
import module1 as m1
import module2 as m2
That is, import the modules (not their contents), but under shorter names. You
can then still access numpy stuff with something like `np.add`, which adds
only three characters of typing but guards against name clashes among
different modules.
|
Python: Connect 4 with TKinter
Question: Alrighty I'm trying to implement a GUI for a game of Connect Four by using
TKinter. Now I have the grid and everything set up what I'm having trouble
with is getting the chip to show up on the board.
Here is my output: 
What I'm trying to do is make it so when I click one of the bottom column
buttons a chip appears (and since this is connect four it should go from
bottom to top)
Here is my code:
from Tkinter import *
from connectfour import *
from minimax import *
from player import *
import tkMessageBox
class ConnectFourGUI:
def DrawGrid(self):
for i in range(0,self.cols+1):
self.c.create_line((i+1)*self.mag,self.mag,\
(i+1)*self.mag,(self.rows+1)*self.mag)
for i in range(0,self.rows+1):
self.c.create_line(self.mag,(i+1)*self.mag,\
self.mag*(1+self.cols),(i+1)*self.mag)
def __init__(self,wdw):
wdw.title("Connect Four")
self.mag = 60
self.rows = 6
self.cols = 7
self.c = Canvas(wdw,\
width=self.mag*self.cols+2*self.mag,\
height = self.mag*self.rows+2*self.mag,\
bg='white')
self.c.grid(row=1,column=1,columnspan=2)
rlabel=Label(root, text="Player1:")
rlabel.grid(row=0,column=0)
self.player1_type=StringVar(root)
options= ["Human", "Random", "Minimax"]
self.player1_type.set(options[2])
self.rowbox=OptionMenu(root, self.player1_type, *options)
self.rowbox.grid(row=0, column=1)
rlabel2=Label(root, text="Player2:")
rlabel2.grid(row=0,column=2)
self.player2_type=StringVar(root)
self.player2_type.set(options[0])
self.rowbox=OptionMenu(root, self.player2_type, *options)
self.rowbox.grid(row=0, column=3)
begin=Button(root, text="Start", command=self.game_start)
begin.grid(row=0, column=4)
self.c.grid(row=1, column=0, columnspan=7)
play_col=[]
for i in range(self.cols):
play_col.append(Button(root, text= "Col %d" %i, command=lambda col= i: self.human_play(col)))
play_col[i].grid(row=10,column="%d"%i)
## self.DrawCircle(1,1,1)
## self.DrawCircle(2,2,1)
## self.DrawCircle(5,3,2)
self.DrawGrid()
self.brd = ConnectFour()
def game_start(self):
self.board=ConnectFour()
print self.player1_type.get()
print self.player2_type.get()
if self.player1_type.get()=="Random":
self.player1 = RandomPlayer(playernum=1)
if self.player2_type.get()== "Random" or self.player2_type.get() == "Minimax":
tkMessageBox.showinfo("Bad Choice", "You Have to choose At least 1 Human Player")
else:
self.player
elif self.player1_type.get()=="Minimax":
self.player1=MinimaxPlayer(playernum=2, ply_depth=4, utility=SimpleUtility(5,1))
if self.player2_type.get()== "Random" or self.player2_type.get() == "Minimax":
tkMessageBox.showinfo("Bad Choice", "You Have to choose At least 1 Human Player")
elif self.player1_type.get()=="Human":
self.player1=Human(playernum=1)
if self.player2_type.get()=="Human":
self.player2=Human(playernum=2)
elif self.player2_type.get()=="Random":
self.player2=RandomPlayer(playernum=2)
elif self.player2_type.get()=="Minimax":
self.player2=MinimaxPlayer(playernum=2, ply_depth=4, utility=SimpleUitlity(5,1))
#self.currentplayer==1
#self.draw()
def human_play(self, col):
if self.player1_type.get()=="Human" and self.player2_type.get() =="Human":
while True:
self.DrawCircle(row,col,1)
if self.brd.is_game_over() is None:
self.DrawCircle(row,col,2)
if self.brd.is_game_over() is None:
pass
else:
print "Player 2 wins!"
break
else:
print "Player 1 wins!"
break
def DrawCircle(self,row,col,player_num):
if player_num == 1:
fill_color = 'red'
elif player_num == 2:
fill_color = 'black'
#(startx, starty, endx, endy)
self.c.create_oval(col*self.mag,row*self.mag,(col+1)*self.mag,(row+1)*self.mag,fill=fill_color)
root=Tk()
ConnectFourGUI(root)
root.mainloop()
I know I'm supposed to call the DrawCircle function in the Human Play
function, I'm just unsure as to how I'm supposed to set it all up. any advice
as to how I could go about this would be greatly appreciated!
Answer: Your code is depending on a few packages I don't have, so I can't be more
specific, but the way I'd go about doing something like this is to track the X
and Y coords of the chip works out the the row and column that it'd go into in
the widget.
You'll need to create a location object, a tuple maybe, and then a way to
translate the location object into a drawable location. Then it's just a
matter of incrementing either X or Y and detecting if there's a chip below it.
|
im trying to get proxies using regex python out of a web page
Question:
import urllib.request
import re
page = urllib.request.urlopen("http://www.samair.ru/proxy/ip-address-01.htm").read()
re.findall('\d+\.\d+\.\d+\.\d+', page)
i dont understand why it says:
File "C:\Python33\lib\re.py", line 201, in findall return _compile(pattern,
flags).findall(string) TypeError: can't use a string pattern on a bytes-like
object
Answer:
import urllib
import re
page = urllib.urlopen("http://www.samair.ru/proxy/ip-address-01.htm").read()
print re.findall('\d+\.\d+\.\d+\.\d+', page)
Worked and gave me the result:
['056.249.66.50', '100.44.124.8', '103.31.250.115', ...
**Edit**
* This works for python2.7
|
Printing and editing multiple lists in python
Question: Im trying to create a small text based game, and to achieve this I am created
20 lists, added 75 spaces to fill the lists, then printed each of the lists
one at a time, all at the same time. I was hoping to then be able to edit the
lists at certain positions so that when the lists were printed again, the
console would display text where I placed it. This is what I came up with so
far...
The desired effect was to have the console print this:
============================
= =
= TEXT ADVENTURE: =
= WAR OF ZE MONSTERS =
= =
============================
But instead I get this:
===========================
I don't know exactly what is happening with my draw function or my write
function but (to me) it would seem as if it should work.
Any help would be amazing as I am relatively new to python. Thanks in advance!
import time
#
# Joel Williams
#
# Purpose: Create a Working Text Engine
#
# start of classes
class line():
def __init__(self):
counter = 0
self.list = []
while (counter != lineSize):
self.list.append(' ')
counter = counter + 1
class cursor():
def __init__(self):
self.cursorPosY = 0
self.cursorPosX = 0
self.cursorPos = [self.cursorPosY, self.cursorPosX]
def setCursorPos(self,y,x):
self.cursorPosY = y
self.cursorPosX = x
self.cursorPos = [self.cursorPosY, self.cursorPosX]
# end of cursor class
# start of peliminary declarations
lineSize = 74
term = cursor()
_1 = line()
_2 = line()
_3 = line()
_4 = line()
_5 = line()
_6 = line()
_7 = line()
_8 = line()
_9 = line()
_10 = line()
_11 = line()
_12 = line()
_13 = line()
_14 = line()
_15 = line()
_16 = line()
_17 = line()
_18 = line()
_19 = line()
_20 = line()
# end of preliminary declarations
# start of preliminary functions
def delLine(x):
del x[:]
counter = 0
x = []
while (counter != lineSize):
x.append(' ')
counter = counter + 1
def clear():
# clears all lists
delLine(_1.list)
delLine(_2.list)
delLine(_3.list)
delLine(_4.list)
delLine(_5.list)
delLine(_6.list)
delLine(_7.list)
delLine(_8.list)
delLine(_9.list)
delLine(_10.list)
delLine(_11.list)
delLine(_12.list)
delLine(_13.list)
delLine(_14.list)
delLine(_15.list)
delLine(_16.list)
delLine(_17.list)
delLine(_18.list)
delLine(_19.list)
delLine(_20.list)
def clearLine():
if(term.cursorPosY == 0):
delLine(_1.list)
elif(term.cursorPosY == 1):
delLine(_2.list)
elif(term.cursorPosY == 2):
delLine(_3.list)
elif(term.cursorPosY == 3):
delLine(_4.list)
elif(term.cursorPosY == 4):
delLine(_5.list)
elif(term.cursorPosY == 5):
delLine(_6.list)
elif(term.cursorPosY == 6):
delLine(_7.list)
elif(term.cursorPosY == 7):
delLine(_8.list)
elif(term.cursorPosY == 8):
delLine(_9.list)
elif(term.cursorPosY == 9):
delLine(_10.list)
elif(term.cursorPosY == 10):
delLine(_11.list)
elif(term.cursorPosY == 11):
delLine(_12.list)
elif(term.cursorPosY == 12):
delLine(_13.list)
elif(term.cursorPosY == 13):
delLine(_14.list)
elif(term.cursorPosY == 14):
delLine(_15.list)
elif(term.cursorPosY == 15):
delLine(_16.list)
elif(term.cursorPosY == 16):
delLine(_17.list)
elif(term.cursorPosY == 17):
delLine(_18.list)
elif(term.cursorPosY == 18):
delLine(_19.list)
elif(term.cursorPosY == 19):
delLine(_20.list)
def draw():
# draws the lists
# each lists is a line (Y)
# each of the list's properties are the text (X)
i1 = ''.join(_1.list)
i2 = ''.join(_2.list)
i3 = ''.join(_3.list)
i4 = ''.join(_4.list)
i5 = ''.join(_5.list)
i6 = ''.join(_6.list)
i7 = ''.join(_7.list)
i8 = ''.join(_8.list)
i9 = ''.join(_9.list)
i10 = ''.join(_10.list)
i11 = ''.join(_11.list)
i12 = ''.join(_12.list)
i13 = ''.join(_13.list)
i14 = ''.join(_14.list)
i15 = ''.join(_15.list)
i16 = ''.join(_16.list)
i17 = ''.join(_17.list)
i18 = ''.join(_18.list)
i19 = ''.join(_19.list)
i20 = ''.join(_20.list)
print i1
print i2
print i3
print i4
print i5
print i6
print i7
print i8
print i9
print i10
print i11
print i12
print i13
print i14
print i15
print i16
print i17
print i18
print i19
print i20
print i20
def write(str):
# changes the lists
c = 0
for i in str:
if term.cursorPosX > lineSize:
term.cursorPosX = 0
if term.cursorPosY > 19:
term.cursorPosY = 0
else:
term.cursorPosY = term.cursorPosY + 1
if term.cursorPosY is 0:
_1.list[term.cursorPosX] = str[c]
c = c + 1
term.cursorPosX = term.cursorPosX + 1
elif term.cursorPosY is 1:
_1.list[term.cursorPosX] = str[c]
c = c + 1
term.cursorPosX = term.cursorPosX + 1
elif term.cursorPosY is 2:
_1.list[term.cursorPosX] = str[c]
c = c + 1
term.cursorPosX = term.cursorPosX + 1
elif term.cursorPosY is 3:
_1.list[term.cursorPosX] = str[c]
c = c + 1
term.cursorPosX = term.cursorPosX + 1
elif term.cursorPosY is 4:
_1.list[term.cursorPosX] = str[c]
c = c + 1
term.cursorPosX = term.cursorPosX + 1
elif term.cursorPosY is 5:
_1.list[term.cursorPosX] = str[c]
c = c + 1
term.cursorPosX = term.cursorPosX + 1
elif term.cursorPosY is 6:
_1.list[term.cursorPosX] = str[c]
c = c + 1
term.cursorPosX = term.cursorPosX + 1
elif term.cursorPosY is 7:
_1.list[term.cursorPosX] = str[c]
c = c + 1
term.cursorPosX = term.cursorPosX + 1
elif term.cursorPosY is 8:
_1.list[term.cursorPosX] = str[c]
c = c + 1
term.cursorPosX = term.cursorPosX + 1
elif term.cursorPosY is 9:
_1.list[term.cursorPosX] = str[c]
c = c + 1
term.cursorPosX = term.cursorPosX + 1
elif term.cursorPosY is 10:
_1.list[term.cursorPosX] = str[c]
c = c + 1
term.cursorPosX = term.cursorPosX + 1
elif term.cursorPosY is 11:
_1.list[term.cursorPosX] = str[c]
c = c + 1
term.cursorPosX = term.cursorPosX + 1
elif term.cursorPosY is 12:
_1.list[term.cursorPosX] = str[c]
c = c + 1
term.cursorPosX = term.cursorPosX + 1
elif term.cursorPosY is 13:
_1.list[term.cursorPosX] = str[c]
c = c + 1
term.cursorPosX = term.cursorPosX + 1
elif term.cursorPosY is 14:
_1.list[term.cursorPosX] = str[c]
c = c + 1
term.cursorPosX = term.cursorPosX + 1
elif term.cursorPosY is 15:
_1.list[term.cursorPosX] = str[c]
c = c + 1
term.cursorPosX = term.cursorPosX + 1
elif term.cursorPosY is 16:
_1.list[term.cursorPosX] = str[c]
c = c + 1
term.cursorPosX = term.cursorPosX + 1
elif term.cursorPosY is 17:
_1.list[term.cursorPosX] = str[c]
c = c + 1
term.cursorPosX = term.cursorPosX + 1
elif term.cursorPosY is 18:
_1.list[term.cursorPosX] = str[c]
c = c + 1
term.cursorPosX = term.cursorPosX + 1
elif term.cursorPosY is 19:
_1.list[term.cursorPosX] = str[c]
c = c + 1
term.cursorPosX = term.cursorPosX + 1
def writf(str,y,x):
write(str)
term.setCursorPos(y,x)
def ask(x):
i = raw_input(x)
return i
def wait(i):
time.sleep(i)
def cursorPos(y,x):
term.setCursorPos(y,x)
# end of preliminary functions
# start of actual stuff
# start of Main Stuff
# start of game functions
def startScreen():
writf('============================ ',8,10)
writf('= = ',9,10)
writf('= TEXT ADVENTURE: = ',10,10)
writf('= WAR OF ZE MONSTERS = ',11,10)
writf('= = ',10,10)
writf('============================ ',12,10)
draw()
wait(5)
# end of game functions
def Main():
startScreen()
Main()
# end of Stuff
# end of actual stuff
Answer: If you want to manage a text based "screen", you would be better off using the
curses module. This is designed exactly for what you want, though it is
somewhat complicated. Also, you could make your program about eighteen times
shorter by using more functions, because you are repeating the same code many
times.
|
scikit-learn svm import error
Question: I'm running [ Canopy ](https://enthought.com/products/canopy/) 64-bit on a
mac. After installing scikit-learn (using the package manager), I tried to
import svm, and got the following error.
ImportError: dlopen(/Users/johnsaccount/Library/Enthought/Canopy_64bit/User/lib/python2.7/site-packages/sklearn/svm/liblinear.so, 2): Library not loaded: /System@rpath/libBLAS.dylib
Referenced from:
/Users/johnsaccount/Library/Enthought/Canopy_64bit/User/lib/python2.7/site-
packages/sklearn/svm/liblinear.so Reason: image not found
Any ideas on what might be the problem?
Answer: Jsen,
My apologies for this error, it was my mistake when building that egg. The
update should now be available and fix that error (the fixed version is
0.13.1-3, both 0.13.1-1 and 0.13.1-2 are broken on os x).
|
restart apache every 12 hours using linux service and python file
Question: Hi i want to use this for restart apache service every 12 hours and i put the
file `apache_rest` in `/etc/init.d/apache_rest` i run but get some error :
[root@localhost init.d]# service apache_rest start
Starting server
/etc/init.d/apache_rest: line 13: /sbin/start-stop-daemon: No such file or directory
apache_rest file:
#!/bin/bash
WORK_DIR="/var/lib/foo"
DAEMON="/usr/bin/python"
ARGS="/home/lol/apache.py"
PIDFILE="/var/run/foo.pid"
USER="foo"
case "$1" in
start)
echo "Starting server"
mkdir -p "$WORK_DIR"
/sbin/start-stop-daemon --start --pidfile $PIDFILE \
--user $USER --group $USER \
-b --make-pidfile \
--chuid $USER \
--exec $DAEMON $ARGS
;;
stop)
echo "Stopping server"
/sbin/start-stop-daemon --stop --pidfile $PIDFILE --verbose
;;
*)
echo "Usage: /etc/init.d/$USER {start|stop}"
exit 1
;;
esac
exit 0
and the python file :
#!/usr/bin/python
import os,signal,time,multiprocessing
stop_event = multiprocessing.Event()
def stop(signum, frame):
stop_event.set()
signal.signal(signal.SIGTERM, stop)
if __name__ == '__main__':
while not stop_event.is_set():
os.system('service httpd restart')
time.sleep(43200)
thanks ^_^
Answer: Simply add this line to root's crontab:
0 1,13 * * * /etc/init.d/httpd restart
You don't need such a convoluted solution.
|
Releasing memory of huge numpy array in IPython
Question: _UPDATE:- This problem solved itself after a machine reboot. Not yet able to
figure out why this error was happening before._
I have a function that loads a huge numpy array (~ 980MB) and returns it.
When I first start Ipython and call this function, it loads the array into the
variable without any problem.
But if I run the same command again, it exits raising a "Memory Error".
I tried the following,
del hugeArray
Still the same error was occurring. I even tried the following
del hugeArray
gc.collect()
gc.collect()
Initially, `gc.collect()` returned 145 and the second call returned 48. But
even after this when I call the function, it was still raising a Memory error.
The only way I could load again was to restart ipython. Is there something I
can do to free all memory in ipython, so that I don't have to restart it?
\----------------Update
Following is the output of `%whos`
Variable Type Data/Info
------------------------------
gc module <module 'gc' (built-in)>
gr module <module 'Generate4mRamp' <...>rom 'Generate4mRamp.pyc'>
np module <module 'numpy' from '/us<...>ages/numpy/__init__.pyc'>
plt module <module 'matplotlib.pyplo<...>s/matplotlib/pyplot.pyc'>
Out of this, gr is my module containing the function which i used to load the
data cube.
\---------How to Reproduce the error
The following simple function is able to reproduce the error.
import numpy as np
import gc
def functionH():
cube=np.zeros((200,1024,1024))
return cube
testcube=functionH() #Runs without any issue
del testcube
testcube=functionH() # Raises Memory Error
del testcube
gc.collect()
gc.collect()
testcube=functionH() # Still Raises Memory Error
**This error is occurring only in Ipython. In simple python (>>>) after
giving`del testcube`, there is no Memory Error.**
Answer: Are you looking at the value? IPython caches output variables as e.g.
`Out[8]`, so if you examine it, it will be kept in memory.
You can do `%xdel testcube` to delete the variable and remove it from
IPython's cache. Alternatively, `%reset out` or `%reset array` will clear
either all your output history, or only references to numpy arrays.
|
Changes to a Gmail notification script
Question: After a long search I've found [this python
script](https://github.com/gevermann/gmail-iphone-
push/blob/master/server/server.py) that does what I need in order to get a
real time notification to my iOS app when a new email arrives. I usually write
in Objective-c and this is the first time I'm dealing with `Python`. Before
I'll try to setup and run the script I'd like to understand it a bit better.
This is the part that I'm not sure about:
# Because this is just an example, exit after 8 hours
time.sleep(8*60*60)
#finally:
# Clean up.
idler.stop()
idler.join()
M.close()
# This is important!
M.logout()
My questions:
1. Should I comment out `time.sleep(8*60*60)` If I want to keep the connection active at all times?
2. What's the use for the Clean up section? Do I need it if I want to keep the connection?
3. Why `M.logout()` is important?
The main question that includes all the above is What changes (if any) I need
to do to this script in order for it to function without stoping or timing
out.
Thanks
Answer: The script has started another thread, the actual work is done in this other
thread. For some reason the main thread is left without anything to do, that's
why the author has put the time.sleep(8*60*60) to occupy it for a while.
If you want to keep the connection active at all times you need to uncomment
the `try:`/`finally:`, see bellow.
If you are new to python beware that indentation is used to define blocks of
code. The cleanup part might actually not be useful if you don't plan to stop
the program, but with the `try:`/`finally:` the cleanup code will be executed
even if you stop the program with Ctrl+C.
Not tested:
# Had to do this stuff in a try-finally, since some testing
# went a little wrong.....
try:
# Set the following two lines to your creds and server
M = imaplib2.IMAP4_SSL("imap.gmail.com")
M.login(USER, PASSWORD)
# We need to get out of the AUTH state, so we just select
# the INBOX.
M.select("INBOX")
numUnseen = getUnseen()
sendPushNotification(numUnseen)
#print M.status("INBOX", '(UNSEEN)')
# Start the Idler thread
idler = Idler(M)
idler.start()
# Sleep forever, one minute at a time
while True:
time.sleep(60)
finally:
# Clean up.
idler.stop()
idler.join()
M.close()
# This is important!
M.logout()
|
Python non-int float
Question: Alright so I have beat my head over my desk for a few days over this one and I
still cannot get it I keep getting this problem:
Traceback (most recent call last):
File "C:\Program Files (x86)\Wing IDE 101 4.1\src\debug\tserver\_sandbox.py", line 44, in <module>
File "C:\Program Files (x86)\Wing IDE 101 4.1\src\debug\tserver\_sandbox.py", line 35, in main
File "C:\Program Files (x86)\Wing IDE 101 4.1\src\debug\tserver\_sandbox.py", line 15, in __init__
builtins.TypeError: can't multiply sequence by non-int of type 'float'
over and over. I think I have hit the wall and really I have done a ecent
amount of looking and testing but if anyone could point me in teh right
direction it would be greatly appreciated.
from math import pi, sin, cos, radians
def getInputs():
a = input("Enter the launch angle (in degrees): ")
v = input("Enter the initial velocity (in meters/sec): ")
h = input("Enter the initial height (in meters): ")
t = input("Enter the time interval between position calculations: ")
return a,v,h,t
class Projectile:
def __init__(self, angle, velocity, height):
self.xpos = 0.0
self.ypos = height
theta = pi *(angle)/180
self.xvel = velocity * cos(theta)
self.yvel = velocity * sin(theta)
def update(self, time):
self.xpos = self.xpos + time * self.xvel
yvel1 = self.yvel - 9.8 * time
self.ypos = self.ypos + time * (self.yvel + yvel1) / 2.0
self.yvel = yvel1
def getY(self):
"Returns the y position (height) of this projectile."
return self.ypos
def getX(self):
"Returns the x position (distance) of this projectile."
return self.xpos
def main():
a, v, h, t = getInputs()
cball = Projectile(a, v, h)
zenith = cball.getY()
while cball.getY() >= 0:
cball.update(t)
if cball.getY() > zenith:
zenith = cball.getY()
print ("/n Distance traveled: {%0.1f} meters." % (cball.getY()))
print ("The heighest the cannon ball reached was %0.1f meters." % (zenith))
if __name__ == "__main__": main()
Answer: Your input functions return strings, not numeric types. You need to convert
them to integers or floats first as appropriate.
I think the particular error you're seeing is when you try to calculate theta.
You multiply pi (a floating-point number) by angle (which holds a string). The
message is telling you that you can't multiply a string by a float, but that
you could multiply a string by an int. (E.g. `"spam" * 4` gives you
`"spamspamspamspam"`, but `"spam" * 3.14` would make no sense.) Unfortunately,
that's not a very helpful message, because for you it's not pi that's the
wrong type, but angle, which should be a number.
You should be able to fix this by changing getInputs:
def getInputs():
a = float(input("Enter the launch angle (in degrees): "))
v = float(input("Enter the initial velocity (in meters/sec): "))
h = float(input("Enter the initial height (in meters): "))
t = float(input("Enter the time interval between position calculations: "))
return a,v,h,t
* * *
I should also note that this is an area where Python 2.* and Python 3.* have
different behaviour. In Python 2.* , `input` read a line of text and then
evaluated it as a Python expression, while `raw_input` read a line of text and
returned a string. In Python 3.* , `input` now does what `raw_input` did
before - reads a line of text and returns a string. While the 'evaluate it as
an expression' behaviour could be helpful for simple examples, it was also
dangerous for anything but a trivial example. A user could type in any
expression at all and it would be evaluated, which could do all sorts of
unexpected things to your program or computer.
|
Python, using ctypes to create C++ class wrapper
Question: I'm well aware that there is no standard ABI for c++, so this is what I did:
//trialDLL.h
#ifndef TRIALDLL_H_
#define TRIALDLL_H_
class MyMathFuncs
{
private:
double offset;
public:
MyMathFuncs(double offset);
~MyMathFuncs();
double Add(double a, double b);
double Multiply(double a, double b);
double getOffset();
};
#ifdef __cplusplus
extern "C"{
#endif
#ifdef TRIALDLL_EXPORT
#define TRIALDLL_API __declspec(dllexport)
#else
#define TRIALDLL_API __declspec(dllimport)
#endif
TRIALDLL_API MyMathFuncs* __stdcall new_MyMathFuncs(double offset);
TRIALDLL_API void __stdcall del_MyMathFuncs(MyMathFuncs *myMath);
TRIALDLL_API double __stdcall MyAdd(MyMathFuncs* myMath, double a, double b);
#ifdef __cplusplus
}
#endif
#endif
And the definition .cpp: (Other class functions' definitions are omitted)
//trialDLL.cpp
#include "trialDLL.h"
MyMathFuncs* __stdcall new_MyMathFuncs(double offset)
{
return new MyMathFuncs(offset);
}
void __stdcall del_MyMathFuncs(MyMathFuncs *myMath)
{
myMath->~MyMathFuncs();
}
double __stdcall MyAdd(MyMathFuncs *myMath, double a, double b)
{
return myMath->Add(a, b);
}
// class functions
double MyMathFuncs::Add(double a, double b)
{
return a+b+ this->offset;
}
And I build this into a dll and named it trialDLL3.dll. Then in python, I
wrote a module as:
#trialDLL3.py
import ctypes
from ctypes import WinDLL
class MyMath(object):
def __init__(self, offset):
self.FunMath = WinDLL('trialDLL3.dll')
self.FunMath.new_MyMathFuncs.argtypes = [ctypes.c_double]
self.FunMath.new_MyMathFuncs.restype = ctypes.c_void_p
self.FunMath.MyAdd.argtypes = [ctypes.c_void_p, \
ctypes.c_double, ctypes.c_double]
self.FunMath.MyAdd.restype = ctypes.c_double
self.obj = self.FunMath.new_MyMathFuncs(offset)
def FunAdd(self, a, b):
self.FunMath.MyAdd(self.obj, a, b)
def delete():
self.FunMath.del_MyMathFuncs()
After all these, strange things happened. In the IDLE python shell, I did:
theMath = MyMath(3.3) #create the instance
theMath.FunAdd(3.3, 3.3) #call the function
The second line returned None instead of 9.9. Then I tried another way round,
putting this line in the shell:
theMath.FunMath.MyAdd(theMath.obj, 3.3 ,3.3)
And this line returns me an unsurprising 9.9, but surprising when compared to
the last result None. Shouldn't these two lines identical? And I decided to
run all those lines explicitly in python shell and see what can go wrong,
writing: (excluding the imports)
loadedDLL = WinDLL('trialDLL3.dll')
loadedDLL.new_MyMathFuncs.argtypes = [ctypes.c_double]
loadedDLL.new_MyMathFuncs.restype = ctypes.c_void_p
loadedDLL.MyAdd.argtypes = [ctypes.c_void_p, \
ctypes.c_double, ctypes.c_double]
loadedDLL.MyAdd.restype = ctypes.c_double
obj = loadedDLL.new_MyMathFuncs(3.3)
FunMath.MyAdd(obj, 3.3, 3.3)
All these lines finally returned 9.9. Aren't these lines identical to the two
lines if the trialDLL3.py module is imported?
theMath = MyMath(3.3) #create the instance
theMath.FunAdd(3.3, 3.3) #call the function
If they are the same deal, why the two line class version returns None and the
explicit way return expected 9.9? Thanks in advance!
Answer: Everything works fine... but you forgot to pass along the return value of the
C function in the method MyMath.FunAdd!
def FunAdd(self, a, b):
return self.FunMath.MyAdd(self.obj, a, b)
^^^^^^
|
How to get a row from coo_matrix as a dense vector in Python?
Question: I'm new to Python and could you help me about some basic sparse matrix
operation:
1. How to extract a dense row vector from a sparse matrix without make the whole matrix dense beforehand? `coo_matrix.getrow()` only returns a sparse representation
2. How to extract a proportion of rows (say, 80%) randomly from a sparse matrix? I need to use them as training data and the proportion left as test data.
Thanks in advance!
Answer: 1. `coo_matrix.getrow().todense()`
2. Use a different sparse representation that supports slicing, for example `csr_matrix`. For sparse matrix A, A[i] will give the ith row.
For example:
In [9]: from random import sample
In [10]: A = csr_matrix(...)
In [11]: n = A.shape[0]
In [12]: indices = sample(range(n), 4*n/5)
In [13]: A[indices].todense()
|
Restrictions in terms of using external libraries (Python) in a Storm Bolt
Question: I want to implement a Bolt (<https://github.com/nathanmarz/storm>) that does
some heavy processing on a tuples using scikit Machine Learning API
(<http://scikit-learn.org/>)
For example -
from sklearn import decomposition
from sklearn import datasets
trans_corpus = vectorizer.fit_transform(corpus)
tfidf = text.TfidfTransformer().fit_transform(trans_corpus)
...
...
Is this possible ? Is having sklearn and all it's dependencies installed on
each node in the cluster enough?
Answer: Theoretically, it should be possible unless there is something really weird
about scikit I don't know. You just need to build your topologies such that
you can write your bolts in Python, which I suspect you already know is
possible and there are plenty of examples.
|
Python : efficient bytearray incrementation
Question: How to iterate all possible values of `bytearray of length = n` in Python ? in
worst case `n <= 40bytes`
For example, iterate for `n = 4` :
00000000 00000000 00000000 00000000
00000000 00000000 00000000 00000001
00000000 00000000 00000000 00000010
.
.
.
.
11111111 11111111 11111111 11111110
11111111 11111111 11111111 11111111
Answer: You can use `itertools.product`:
In [11]: from itertools import product
In [15]: for x in product('01',repeat=4): #for your n=4 change repeat to 32
print "".join(x)
....:
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
|
Python - variable is getting set to 0 and can't figure out why
Question: Okay, so I'm making a little game with pygame and building the map by
generating tiles to a multidimensional array. In order to do that I'm using
two for loops.
def create(this, t):
if t == "grasslands":
for j in range(0, this.numRows):
for i in range(0, this.numColumns):
this.column.append(this.Tile("grass", j * this.tileWidth, i * this.tileHeight))
this.row.append(this.column)
The value for **j * this.tileWidth** is getting passed into the Tile
initialization correctly. After though the **column[whatever].x** value is
still 0. The **y** value gets set just fine, and if I use **i** or any other
value instead of **j** things work just fine. Is this something I'm doing
wrong or something wonky with Python?
**_mapgen.py_**
import pygame
from sprite import *
from assets import *
class mapG:
def __init__(this, resw, resh):
this.numRows = 3
this.numcolumns = 3
this.tileWidth = 128
this.tileHeight = 128
this.row = []
this.column = []
this.width = this.numRows * this.tileWidth
this.height = this.numcolumns * this.tileHeight
def create(this, t):
if t == "grasslands":
for j in range(0, this.numRows):
for i in range(0, this.numcolumns):
this.column.append(this.Tile("grass", j * this.tileWidth, i * this.tileHeight))
this.row.append(this.column)
def tileAt(this, x, y):
pass
def moveRight(this):
for j in range(0,this.numRows):
for i in range(0, this.numcolumns):
this.row[j][i].incX(1)
def Update(this, src):
for j in range(0,this.numRows):
for i in range(0, this.numcolumns):
this.row[j][i].Update(src)
print(this.row[j][i].y, this.row[j][i].x)
class Tile:
def __init__(this, name, xpos, ypos):
this.y = ypos
this.x = xpos
this.image = assets.tile[name + ".png"]
this.sprite = sprite(this.image, this.x, this.y, 100, 100)
def incX(this, amount):
this.sprite.IncX(amount)
def decX(this, amount):
this.sprite.DecX(amount)
def incY(this, amount):
this.sprite.IncY(amount)
def decY(this, amount):
this.sprite.DecY(amount)
def Update(this, src = None):
if src != None:
this.sprite.Update(src)
**_sprite.py_**
import pygame
import assets
class sprite:
def __init__(this, image, xpos, ypos, width = None, height = None):
this.image = image
this.x = xpos
this.y = ypos
this.width = width
this.height = height
if this.width != None and this.height != None:
this.image = pygame.transform.scale(image, (this.width,this.height))
def GetPos(this):
return (this.x, this.y)
def IncX(this, amount):
this.x += amount
def IncY(this, amount):
this.y += amount
def DecX(this, amount):
this.x -= amount
def DecY(this, amount):
this.y -= amount
def Update(this, src = None):
if src != None:
src.blit(this.image, this.GetPos())
Answer: I believe the issue you have comes from your use of the `this.column` variable
in the `create` method.
You're only creating one column list (in `__init__`) and then reusing it for
all the columns of your map. This won't work.
Your `this.row` list ends up having multiple references to the same column
list, which ends up containing all of the `Tile` objects you create. You only
see some of them later, since your iteration code uses predefined dimensions,
rather than actually iterating over the whole of the lists.
To understand this, try to imagine how the iteration progresses for a 2x2 grid
(ignoring the tile dimensions). I'm putting each `i` and `j` value on it's own
line to show how it progresses, and giving the values of `row` and `columns`
after each step side:
j=0:
i=0:
column.append(Tile(i, j))
# column is [Tile(0, 0)]
# row is []
i=1:
column.append(Tile(i, j))
# column is [Tile(0, 0), Tile(0, 1)]
# row is []
row.append(column)
# column is [Tile(0, 0), Tile(0, 1)]
# row is [[Tile(0, 0), Tile(0, 1)]]
j=1: # column is not reset!
i=0:
column.append(Tile(i, j))
# column is [Tile(0, 0), Tile(0, 1), Tile(1, 0)]
# row is [[Tile(0, 0), Tile(0, 1), Tile(1, 0)]]
i=1:
column.append(Tile(i, j))
# column is [Tile(0, 0), Tile(0, 1), Tile(1, 0), Tile(1, 1)]
# row is [[Tile(0, 0), Tile(0, 1), Tile(1, 0), Tile(1, 1)]]
row.append(column)
# column is [Tile(0, 0), Tile(0, 1), Tile(1, 0), Tile(1, 1)]
# row is [[Tile(0, 0), Tile(0, 1), Tile(1, 0), Tile(1, 1)],
# [Tile(0, 0), Tile(0, 1), Tile(1, 0), Tile(1, 1)]]
The `row` list contains two references to the same `column` list of four
tiles. Your code had intended to add the first two `Tile(0, 0)` and
`Tile(0,1)` to the first column, then the last two tiles `Tile(1, 0)` and
`Tile(1, 1)` to the second column. But because the same list was used both
times, you end up with all the values together, and then the whole bunch
repeated. When you iterate, you're only seeing the repeated values on the left
part of the diagram above.
Here's how to fix it:
def create(this, t):
if t == "grasslands":
for j in range(0, this.numRows):
column = [] # Create a new list! This is the key!
for i in range(0, this.numColumns):
column.append(this.Tile("grass",
j * this.tileWidth,
i * this.tileHeight))
this.row.append(column)
You can get rid of the line in the constructor that initializes `self.column`
too. It's only needed temporarily, so there's no need to use an instance
variable.
|
Ascii codec cannot decode HTML when saving to file in python
Question: I have a text that is part of html. I would like to save it to a file.
This works fine in debug mode in Eclipse, but fails on runtime from shell. I
am using a short example of html that fails.
xx = '<input type="hidden" name="charset_test" value="€,´,€,´,水,Д,Є" />'
with codecs.open('myfile.htm'), 'wb', encoding="utf-8") as output:
output.write(data)
and I get:
Exception 'ascii' codec can't decode byte 0xe2 in position XXX: ordinal not in range(128)
where XXX is the position in the relevant file of the "strange" symbols, such
as the EURO sign.
Why is this working from Eclipse and not from shell? How do I solve this?
I tried
HTMLParser.HTMLParser().unescape()
unquote()
unicode()
Nothing worked...
Answer: The following code works for me...
# coding=utf-8
import codecs
data = '<input type="hidden" name="charset_test" value="€,´,€,´,水,Д,Є" />'
with codecs.open('myfile.htm', 'wb', encoding="utf-8") as output:
output.write(data.decode('utf-8'))
...but if the source data is already UTF-8 encoded, and you also want to write
UTF-8 data, there's no need to decode it to a Python `unicode` object, then
re-encode back to UTF-8. You can just do...
# coding=utf-8
data = '<input type="hidden" name="charset_test" value="€,´,€,´,水,Д,Є" />'
with open('myfile.htm', 'wb') as output:
output.write(data)
|
Read numeric value from txt. file and compare it to condition Python
Question: I'm new to Python and working on final project for my degree. I want to write
a Python script which will read numeric value (like: 21, 23, 28 etc.) and
compare it to value in the script. If the value matches it should execute
another python script. Everything seem to work correctly, but the red value
from file make no change in conditions matching. The script every time
executes statement ELSE instead of IF while the condition is really true.
Here is my code:
import time
import sys
import os
check_period = 2
fo = open("/home/pi/thermometer1.txt", "r+")
str = fo.readline();
fo.close()
while True:
fo = open("/home/pi/thermometer1.txt", "r+")
str = fo.readline();
if str < 25 :
os.system("python /home/pi/servo/servo1/servo6.py")
print str
fo.close()
else:
os.system("python /home/pi/servo/servo1/servo1.py")
print str
fo.close()
time.sleep(check_period)
One more question would be how to edit this script which will compare one .txt
file with numeric value like. 23 to other .txt file with numeric value like.
27 and if condition is met execute another python script (similar like the
code above). Thanks in advance for all comments.
Answer: Reading from the file you get strings, not integers. Since they're different
(non-comparible) types, any comparison you do result in a consistent, but
arbitrary value based on the types1. Apparently, strings are considered
greater than integers (for Cpython -- Other implementations might behave
differently).
You need to construct an integer out of your string instead:
int_from_str = int(fo.readline())
* * *
While we're at it, there are much better ways to iterate over a file:
with open("/home/pi/thermometer1.txt") as fin:
for line in fin:
int_from_str = int(fin)
...
1On python3.x, any comparison other than `==` will raise an exception.
|
Python: loop through several csv files
Question: I was wondering if anybody knew how I could change a script in Python so it
goes through a folder containing csv files and takes them in groups of three.
The script is working when I type the file names in the command line, but I've
got lots of files, so that would take forever. It looks like this now:
resultsdir = "blah"
#filename1=sys.argv[1]
#filename2=sys.argv[2]
#filename3=sys.argv[3]
file1 = open(resultsdir+"/"+filename1+".csv")
file2 = open(resultsdir+"/"+filename2+".csv")
file3 = open(resultsdir+"/"+filename3+".csv")
I'm a complete beginner, I hope I've been able to explain what I want. Cheers
for any help!
Answer: You could use the `glob` module
(<http://docs.python.org/3.3/library/glob.html>) to get all `.csv` files in a
directory and open them then.
**Example:**
import glob
resultsdir = "blah"
files = sorted(glob.glob(resultsdir+'/*.csv'))
while len(files) >= 3:
file1 = open(files.pop(0))
file2 = open(files.pop(0))
file3 = open(files.pop(0))
# Do something
# if the number of files can't be divided by 3 do something
# with the 1 or 2 files which are left
**Edit:** Changed `files.pop()` to `files.pop(0)` to get the files from the
first to the last and not from the last to the first file.
|
devappserver2, remote_api, and --default_partition
Question: To access a remote datastore locally using the original dev_appserver I would
set --default_partition=s as mentioned
[here](http://stackoverflow.com/questions/9280613/badrequesterror-app-
smyapphr-cannot-access-app-devmyapphrs-data-why/9281772#9281772)
In March 2013 Google made devappserver2 the default development server, and it
does not support --default_partition resulting in the original, dreaded:
BadRequestError: app s~appname cannot access app dev~appname's data
It appears like the first few requests are served correctly with
os.environ["APPLICATION_ID"] == 's~appname'
Then a subsequent request results in a call to /_ah/warmup and then
os.environ["APPLICATION_ID"] == 'dev~appname'
The docs specifically mention related topics but appear geared to
dev_appserver
[here](https://developers.google.com/appengine/docs/python/tools/devserver)
> Warning! Do not get the App ID from the environment variable. The
> development server simulates the production App Engine service. One way in
> which it does this is to prepend a string (dev~) to the APPLICATION_ID
> environment variable, which is similar to the string prepended in production
> for applications using the High Replication Datastore. You can modify this
> behavior with the --default_partition flag, choosing a value of "" to match
> the master-slave option in production. Google recommends always getting the
> application ID using the get_application_id() method, and never using the
> APPLICATION_ID environment variable.
Answer: You can do the following dirty little trick:
from google.appengine.datastore.entity_pb import Reference
DEV = os.environ['SERVER_SOFTWARE'].startswith('Development')
def myApp(*args):
return os.environ['APPLICATION_ID'].replace("dev~", "s~")
if DEV:
Reference.app = myApp
|
How to subclass Clock in Pyglet?
Question: I want to subclass Clock class of pyglet.clock module, but I have some
troubles when I use schedule_interval:
The following code doesn't print anything and the object c looks like if not
ticked at all:
#!/usr/bin/env python
# -*- coding: utf-8 -*-
import pyglet
class Clock(pyglet.clock.Clock):
def __init__(self):
super(Clock, self).__init__()
class Test(object):
def update(self, dt):
print dt
w = pyglet.window.Window()
@w.event
def on_draw():
w.clear()
t = Test()
c = pyglet.clock.Clock()
c.schedule_interval(t.update, 1/60.0)
pyglet.app.run()
But the next works fine.
#!/usr/bin/env python
# -*- coding: utf-8 -*-
import pyglet
class Clock(pyglet.clock.Clock):
def __init__(self):
super(Clock, self).__init__()
pyglet.clock.set_default(self)
class Test(object):
def update(self, dt):
print dt
w = pyglet.window.Window()
@w.event
def on_draw():
w.clear()
t = Test()
c = Clock()
c.schedule_interval(t.update, 1/60.0)
pyglet.app.run()
The only difference is the pyglet.clock.set_default(self) sentence in the
constructor method of Clock.
I think this is not clear or, at least, is not the best way of subclassing
pyglet.clock.Clock to have your own derived Clock class.
**The questions:**
There is some way to set the default clock automatically with Pyglet?
There is a solution more elegant or pythonic?
Is possible do this without the pyglet.clock.set_default(self) line?
Answer: I haven't used pyglet, but here's my guess:
You're almost there. The reason your first implementation probably didn't work
is because of these lines:
c = pyglet.clock.Clock()
c.schedule_interval(t.update, 1/60.0)
Here, you are creating a new Clock instance and are scheduling a callback on
it. However, at no point are you actually associating that instance of a clock
with pyglet. So, when you run...
pyglet.app.run()
...you never actually told pyglet about the new clock instance `c`. Instead,
pyglet will use an instance that it made itself. Check out this [source code
for pyglet from the clock
module](https://code.google.com/p/pyglet/source/browse/pyglet/clock.py)...:
# Default clock.
_default = Clock()
def set_default(default):
'''Set the default clock to use for all module-level functions.
By default an instance of `Clock` is used.
:Parameters:
`default` : `Clock`
The default clock to use.
'''
global _default
_default = default
def get_default():
'''Return the `Clock` instance that is used by all module-level
clock functions.
:rtype: `Clock`
:return: The default clock.
When pyglet starts up, it creates its own instance of the clock (called
`_default`). If you want to use your own, you need to use `set_default()` to
replace it. Therefore, to fix your first piece of code, you probably would
need to do one of the following:
c = pyglet.clock.get_default()
c.schedule_interval(t.update, 1/60.0)
...or...
c = pyglet.clock.Clock()
pyglet.clock.set_default(c)
c.schedule_interval(t.update, 1/60.0)
The second example above is pointless: pyglet already gives you an instance of
Clock, so you'd really just duplicating something that pyglet has already done
for you. Either way though, you end up scheduling the callback on the clock
**that pyglet is using**.
So, it should now make sense that, yes, you do need to call `set_default()`.
This is how you tell pyglet to use your object rather than the one it makes by
default. Now, you **could** conceivably put this `set_default()` call where
you currently have it (in the constructor). However, it probably makes more
sense to do this...
class Clock(pyglet.clock.Clock):
def __init__(self):
super(Clock, self).__init__()
...
c = Clock()
pyglet.clock.set_default(c)
**Edit** :
In response to the question of why you would do this outside the constructor:
First, as a general rule of thumb, a constructor should only be used to
construct the object. By adding set_default, you are not only constructing the
object, you are also changing the state of some other entity (the pyglet.clock
module). This can cause confusion, as I will show below. Assume I wrote code
that looked like this...
c = MyClock()
c2 = UnpausedClock()
In this example, I have previously implemented two different clock types:
`NewClock` and `UnpausedClock`. `UnpausedClock` will only consider time to be
passing when the game is unpaused. If I put `set_default()` in the constructor
of these two new classes, then `UnpausedClock` would become the new default
clock (which I don't want). By NOT putting `set_default()` in the constructor,
and instead doing the following:
c = MyClock()
c2 = UnpausedClock()
pyglet.clock.set_default(c)
My code is more explicit, and less confusing.
Of course, the code will work either way, but I feel that having the
set_default OUTSIDE the constructor gives you more flexibility to use the
class as you need to later on.
|
python feedparser ImportError: No module named feedparser
Question: I receive an error when I attempt to include the feedparser library into the
interactive Python environment:
>>>> import feedparser
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: No module named feedparser
This also happens with BeautifulSoup and pydelicious. Why am I getting this
error?
Using OS X 10.8.3, which include the following files in the /usr/bin
directory:
$ ll python*
-rwxr-xr-x 2 root wheel 58896 Mar 17 20:55 python
-rwxr-xr-x 6 root wheel 925 Nov 16 10:30 python-config
lrwxr-xr-x 1 root wheel 75 Nov 16 10:30 python2.5 -> ../../System/Library/Frameworks/Python.framework/Versions/2.5/bin/python2.5
lrwxr-xr-x 1 root wheel 82 Nov 16 10:30 python2.5-config -> ../../System/Library/Frameworks/Python.framework/Versions/2.5/bin/python2.5-config
lrwxr-xr-x 1 root wheel 75 Nov 16 10:30 python2.6 -> ../../System/Library/Frameworks/Python.framework/Versions/2.6/bin/python2.6
lrwxr-xr-x 1 root wheel 82 Nov 16 10:30 python2.6-config -> ../../System/Library/Frameworks/Python.framework/Versions/2.6/bin/python2.6-config
lrwxr-xr-x 1 root wheel 75 Nov 16 10:30 python2.7 -> ../../System/Library/Frameworks/Python.framework/Versions/2.7/bin/python2.7
lrwxr-xr-x 1 root wheel 82 Nov 16 10:30 python2.7-config -> ../../System/Library/Frameworks/Python.framework/Versions/2.7/bin/python2.7-config
-rwxr-xr-x 2 root wheel 58896 Mar 17 20:55 pythonw
lrwxr-xr-x 1 root wheel 76 Nov 16 10:30 pythonw2.5 -> ../../System/Library/Frameworks/Python.framework/Versions/2.5/bin/pythonw2.5
lrwxr-xr-x 1 root wheel 76 Nov 16 10:30 pythonw2.6 -> ../../System/Library/Frameworks/Python.framework/Versions/2.6/bin/pythonw2.6
lrwxr-xr-x 1 root wheel 76 Nov 16 10:30 pythonw2.7 -> ../../System/Library/Frameworks/Python.framework/Versions/2.7/bin/pythonw2.7
Python's location:
$ which python
/usr/bin/python
Python's version:
$ python -V
Python 2.7.2
It was probably unnecessary, but I installed Python with Homebrew:
$ brew install python
Which installed these files:
$ brew list python
/usr/local/Cellar/python/2.7.4/bin/smtpd2.py
/usr/local/Cellar/python/2.7.4/bin/smtpd2.7.py
/usr/local/Cellar/python/2.7.4/bin/smtpd.py
/usr/local/Cellar/python/2.7.4/bin/pythonw2.7
/usr/local/Cellar/python/2.7.4/bin/pythonw2
/usr/local/Cellar/python/2.7.4/bin/pythonw
/usr/local/Cellar/python/2.7.4/bin/python2.7-config
/usr/local/Cellar/python/2.7.4/bin/python2.7
/usr/local/Cellar/python/2.7.4/bin/python2-config
/usr/local/Cellar/python/2.7.4/bin/python2
/usr/local/Cellar/python/2.7.4/bin/python-config
/usr/local/Cellar/python/2.7.4/bin/python
/usr/local/Cellar/python/2.7.4/bin/pydoc2.7
/usr/local/Cellar/python/2.7.4/bin/pydoc2
/usr/local/Cellar/python/2.7.4/bin/pydoc
/usr/local/Cellar/python/2.7.4/bin/pip-2.7
/usr/local/Cellar/python/2.7.4/bin/pip
/usr/local/Cellar/python/2.7.4/bin/idle2.7
/usr/local/Cellar/python/2.7.4/bin/idle2
/usr/local/Cellar/python/2.7.4/bin/idle
/usr/local/Cellar/python/2.7.4/bin/easy_install-2.7
/usr/local/Cellar/python/2.7.4/bin/easy_install
/usr/local/Cellar/python/2.7.4/bin/2to3-2.7
/usr/local/Cellar/python/2.7.4/bin/2to3-2
/usr/local/Cellar/python/2.7.4/bin/2to3
/usr/local/Cellar/python/2.7.4/Build Applet.app/Contents/ (8 files)
/usr/local/Cellar/python/2.7.4/Frameworks/Python.framework/ (4858 files)
/usr/local/Cellar/python/2.7.4/IDLE.app/Contents/ (8 files)
/usr/local/Cellar/python/2.7.4/Python Launcher.app/Contents/ (17 files)
/usr/local/Cellar/python/2.7.4/share/man/ (3 files)
/usr/local/Cellar/python/2.7.4/share/python/ (317 files)
Then I installed feedparser:
$ pip install feedparser
Which resulted in these files:
$ ll /usr/local/lib/python2.7/site-packages/f*
-rw-r--r-- 1 foobar admin 166583 Apr 24 20:16 /usr/local/lib/python2.7/site-packages/feedparser.py
-rw-r--r-- 1 foobar admin 138040 Apr 24 20:16 /usr/local/lib/python2.7/site-packages/feedparser.pyc
I was hoping to avoid these sorts of problems by using Homebrew (which has
worked well with other libraries). What am I missing?
Answer: If your Python is at `/usr/bin/python`, then you are not using the Homebrew-
built Python, but the OS X default one. (Also note the version number
discrepancies in your output.) So any package that you install with `pip` will
be installed into the Homebrew space, but will not be visible to the OS
X-supplied Python installation. (OS X does not supply `pip`, so that's quite
like the Homebrew one.)
The fix for you is quite likely to update your path to have `/usr/local/bin`
come before `/usr/bin`.
|
Controlling MDrive 23 with Python under Linux
Question: MDrive 23 motor takes commands from a terminal, and I got it to work with
screen program:
screen /dev/ttyUSB0
Is this is called a serial terminal? I'm unfamiliar with the details of the
connection, but feel like I should be able to use PySerial to send the
commands.
I tried:
import serial
ser = serial.Serial('/dev/ttyUSB0', 19200)
ser.isOpen() # Returns True
ser.write('ma 100000\r\n') # Does nothing...
ser.inWaiting() # Returns 0
ser.close()
I didn't know how to set the other init variables, like:
parity = serial.PARITY_ODD,
stopbits = serial.STOPBITS_TWO
bytesize = serial.SEVENBITS
I'm going to try guessing some values next... The documentation is lame, but
it mentions MODBUS TCP and Mcode.
How do I set these and are there any syntax errors in my snippet?
I know how to send arguments to the Serial object, but I do not know what
values are typical.
Answer: The other parameters to the Serial constructor are set in a similar way as
port and baudrate:
ser = serial.Serial(port = '/dev/ttyUSB0', baudrate=19200, bytesize=serial.SEVENBITS, parity=serial.PARITY_ODD, stopbits=serial.STOPBITS_TWO)
ser.write('whatever')
ser.flush() # wait for data to be written
ser.close()
* * *
Edit: It [seems](http://motion.schneider-
electric.com/support/knowledge_base.html) the default settings are 9600 baud,
8 bits, no parity and 1 stop bit. In addition no flow-control is used. That
would be equivalent to:
ser = serial.Serial(port = '/dev/ttyUSB0', baudrate=9600, bytesize=serial.EIGHTBITS, parity=serial.PARITY_NONE, stopbits=serial.STOPBITS_ONE, xonxoff=False, rtscts=False, dsrdtr=False)
As all values, except port, are set to their defaults, you may use:
ser = serial.Serial(port = '/dev/ttyUSB0')
The last thing to worry about is which (read) timeout to set. This is
measured/set in seconds (float allowed) and sets how long a read() command
will block before returning what has been read.
|
Using the twitter API and Python to obatain retweeter's id
Question: I have an issue that has been bothering for a while now, and which I have
tried really hard to fix but have found no solution. So I'm doing an
internship doing research on complex networks, nothing business-oriented, it's
mostly physics and network theory research that they are doing. So what I'm
doing is writing scripts for them to obtain data from twitter and tumblr (such
as friend lists, and retweets) and then then graphing the user-to-user
relations.
Anyways, going straight to my problem, I have already written my script pretty
much, mainly using the twitter-python wrapper. However, none of the wrappers
for python has any way of using the GET statuses/retweets/:id which returns
the 100 first retweeter's ids. I've looked through all different twitter
libraries for python and could not find anything. I found tweety for MATLAB
but I'm using Ubuntu and it hasn't been easy to obtain.
So my question is, how can I implement this API myself, without a wrapper? is
there any wrapper, even in another language that you guys would know allows me
to do this? I wouldn't mind getting the retweet information in a file and then
using my python script to go over it and get the information I need.
Thank you very much! This is the resource I wanna use:
<https://dev.twitter.com/docs/api/1.1/get/statuses/retweets/%3Aid>
EDIT: So with tweepy this is what I'm trying to do
auth = tweepy.OAuthHandler(CONSUMER_KEY, CONSUMER_SECRET)
auth.set_access_token(ACCESS_TOKEN, ACCESS_TOKEN_SECRET)
tweet = auth.retweets(TWEET_ID)
print json.dumps(tweet, indent=1)
Answer: Looks like [tweepy](http://pythonhosted.org/tweepy/html/index.html) should
work for you. See
[docs](http://pythonhosted.org/tweepy/html/api.html?highlight=retweet#API.retweets)
and [source](https://github.com/tweepy/tweepy/blob/master/tweepy/api.py#L124).
Example:
import tweepy
auth = tweepy.OAuthHandler(consumer_key, consumer_secret)
auth.set_access_token(key, secret)
api = tweepy.API(auth)
public_tweets = api.search("stackoverflow")
for tweet in public_tweets:
print api.retweets(tweet.id)
Hope that helps.
|
Error using etree in lxml
Question: I want to use xpath in python . I tried
import xml.etree.ElementTree as ET
Since this library has limited usage I had to use lxml after a long session of
search on google. I had several problems during installation and finally i
installed lxml but when i use
from lxml import etree
it throws back an error as below. could you please tell me the solution to
this problem!!!
Traceback (most recent call last):
File "<pyshell#0>", line 1, in <module>
from lxml import etree
ImportError: DLL load failed: %1 is not a valid Win32 application.
Can any1 tell me what the problem would be?? Thanks for assistance!!
Answer: I solved this by downloading the 64-bit version of lxml here:
<https://pypi.python.org/pypi/lxml/3.4.1>
lxml-3.4.1.win-amd64-py2.7.exe
It's the only one that worked to solve the win32 error. You might want to
destroy the old version of lxml before you do this.
|
How to flag end of loop over dictionary with two int's tuple as key - combination-like loop needed
Question: i have in memory a dictionary with the following pattern:
value_refs[tuple([a,b])] = some float value
the dictionary is a pool of all the possible combinations of the values of
4000 references, previously computated (some millions). ex:
...
value_refs[1,4] =0,76543
value_refs[1,5] =0,89734 #i want this value, since it is the bigger of all the second ref's,
# related with the ref. 1 (first tuple in the key)
...
value_refs[1,4000] =0,77543
...
...
value_refs[4000,30] =0,76543
value_refs[4000,31] =1,89734 # I want this value, since it is the bigger of all the second
# references, related with the ref. 4000 (first tuple in the key)
value_refs[4000,32] =0,77543
The problem is that i don't know how to make a loop over the entire dictionary
keys in the same mode as 'combinations' do, using them as iterables, like:
asymptote=0
cache=[]
pool_chain={}
for c in value_refs.keys()[c][0]: # [0] because i need the first tuple value of the key, by rank
for d in value_refs.keys()[d][1]: # [1] because i need a loop over the range of all the second
#tuple values in the dict pool, versus the outer loop
while True:
try:
if value_refs[c,d] > asymptote:
cache=[c,d]
asymptote=value_refs[c,d]
except KeyError:
pass
except StopIteration:
pool_chain[cache]=asymptote
asymptote=0
#and now c would advance by an ordered rank intil the number 4000...
I know that the above code doesn't work, because of bad syntax but i think
that is the best way to post the question. The unordered nature of the
dictionaries in python is (i think) a problem to that nested loops process the
2-tuple keys by an ordered way, like 1,2, 1,3 ... 1,4000 2,3 2,4 and so on.
How can i iterate over my dictionary in memory in an ordered way (by rank) and
extract both the 2-tuple key and the value that is the biggest for the second
value in the key versus the first tuple-value in the same key, and this for
all combinations? Thanks in advance.
Answer: How about a 2D-array with 4000*4000 elements? Takes less memory and is faster
then such a dict. Especially, if you have **all the possible combinations**.
Have a look at [Numpy](http://www.numpy.org/).
import numpy as np
arr = np.empty((4000,4000))
for i, a in enumerate([...]):
for j, b in enumerate([...]):
arr[i, j] = ...
...
for i in arr.shape[0]:
for j in arr.shape[1]:
... arr[i, j]
|
Changing date format after converting from int value in python
Question: Is it possible to change format of date from (YYYY,MM,DD) to (DD,MM,YYYY)..
import datetime
date_value = 41381.0
date_conv= datetime.date(1900, 1, 1) + datetime.timedelta(int(date_value))
print date_conv
output:
date_conv = 2013-04-19
[Converting date formats python - Unusual date formats - Extract
%Y%M%D](http://stackoverflow.com/questions/14271791/converting-date-formats-
python-unusual-date-formats-extract-ymd?answertab=votes#tab-top)
current output is in (YYYY,MM,DD) formate.
Answer:
print date_conv.strftime('%d.%m.%Y')
prints the date in `DD.MM.YYYY` format. More formatting options
[here](http://docs.python.org/2/library/datetime.html#strftime-strptime-
behavior).
|
How to prevent bottle from handling signals
Question: I am building an application using the Bottle web-framework.
I would like to catch signals USR1 and USR2 to do some work aside from the
bottle server. Mainly I want to be able to reload configuration without
shutting down the web server because I want some objects to live on.
I tried to handle the signals (USR1 and USR2) on my own using :
signal.signal(signal.SIGUSR1, my_handler)
The problem is that, upon receiving a sigUSR1, the bottle web server crashes
with the following trace :
Traceback (most recent call last):
File "giomanager.py", line 46, in <module>
run( giomanager, port=60200 )
File "/usr/lib/python2.7/dist-packages/bottle.py", line 2389, in run
server.run(app)
File "/usr/lib/python2.7/dist-packages/bottle.py", line 2087, in run
srv.serve_forever()
File "/usr/lib/python2.7/SocketServer.py", line 225, in serve_forever
r, w, e = select.select([self], [], [], poll_interval)
select.error: (4, 'Interrupted system call')
Do you have an idea why is this happening ? Is it possible to prevent bottle
from receiving those signals ?
Answer: You didn't post your code, so I'm guessing that it might boil down to
something like this:
import signal
from bottle import route, run
def my_handler(*args):
print 'in signal handler', args
signal.signal(signal.SIGUSR1, my_handler)
@route('/hello')
def hello():
return "Hello World!\n"
run(host='localhost', port=8080, debug=True)
Which, incidentally, works for me--it prints "in signal handler."
**But** : what I really wanted to suggest is that you consider another
mechanism altogether for refreshing your data. I've had much success with a
separate refresh thread that repeatedly sleeps for some duration, then wakes
up and polls a certain file (or url) to see if there's new data.
There are several reasons why this might be better than using signals, not
least of which is that it'll be a pain (or impossible) to signal each process
if you ever run multi-process. Besides, you weren't planning on running the
Bottle development server in production, were you? (It's [not
recommended](http://bottlepy.org/docs/dev/deployment.html#server-options) for
anything but the smallest of apps.) Given that, once you run your Bottle app
within another webserver, signal handling becomes tricky.
|
python pandas index is_unique not working
Question: I'm new to python so please call me on not including relevant information.
I've installed python, ipython, and am using the notebook on an Ubuntu
installation in a VM.
I'm working through examples laid out in Wes McKinney's Python for Data
Analysis. After the following import statements:
from pandas import Series, DataFrame
import pandas as pd
I defined a dataframe with:
series1 = Series(range(5), index=['a', 'a', 'b', 'b', 'c'])
And subsequently wanted to test the indexes uniqueness with:
series1.index.is_unique
And get this error:
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
/home/username/<ipython-input-64-e42615bb2da2> in <module>()
----> 1 series1.index.is_unique
AttributeError: 'Index' object has no attribute 'is_unique'
The book indicates this attribute exists. Other stackoverflow questions and
answers reference this attribute.
What am I doing wrong?
Thanks
After being asked what version of pandas I was using, I checked and it was
0.7.0 Upgrading with
pip install --upgrade pandas
Got me where I needed to be.
Answer: Make sure you are using an updated version, no issues here with `0.11.0`:
>>> from pandas import Series, DataFrame
>>> s = Series(range(5), index=['a', 'a', 'b', 'b', 'c'])
>>> s.index.is_unique
False
Either download the most recent version from
[here](https://pypi.python.org/pypi/pandas#downloads), or upgrade from command
line:
pip install --upgrade pandas
For this snippet there's no need to `import pandas as pd` on the second line,
so I've removed it.
|
AttributeError: Extension instance has no attribute '__version__'
Question: Here is the script..
from distutils.core import setup, Extension
nmap = Extension('nmap',sources = ['nmap/nmap.py',
'nmap/__init__.py', 'nmap/example.py'])
from nmap import *
setup (
name = 'python-nmap',
version = nmap.__version__,
author = 'Alexandre Norman',
author_email = '[email protected]',
license ='gpl-3.0.txt',
keywords="nmap, portscanner, network, sysadmin",)
... and i got this error:
Traceback (most recent call last):
File "C:\Python27\nmap.py", line 6, in <module>
from nmap import *
File "C:\Python27\nmap.py", line 17, in <module>
version = nmap.__version__,
AttributeError: Extension instance has no attribute '__version__'
Answer: There are a number of problems here.
1. Your `nmap` package isn't an extension, it's a pure-Python package; don't create an `Extension` object for it. Python extension are written in [C or C++](http://docs.python.org/2/extending/building.html).
2. You're trying to access `nmap.__version__`, presumably because you defined that variable in `nmap/__init__.py`, but `nmap` here is that `Extension` object you created; it's trying to access the variable from the wrong thing.
3. Even if you remove the `Extension` object, you still wouldn't be able to access `nmap.__version__`, because you imported your package incorrectly; you meant to use `import nmap`.
4. You never actually pass your package to `setup`, so `distutils` won't know about it. There are a few examples of how to do that [in the documentation](http://docs.python.org/2/distutils/examples.html#pure-python-distribution-by-package).
The [`distutils` documentation](http://docs.python.org/2/distutils/index.html)
is pretty big, but it's a good idea to read through all of it at least once.
|
Enthought Canopy 64bit on OSX: import pyglet.gl failure
Question: ## Retaining question for posterity; see workaround in edit
The Pyglet package comes installed at base and isn't removable. Using the
current fully updated version 1.1.4 of Pyglet, I get repeatable errors related
to importing the item `pyglet.gl.gl_info`; for instance, upon attempting to
create a `pyglet.window.Window()`, upon trying to `import pyglet.gl`, or upon
attempting to import pygarrayimage via `from pygarrayimage.arrayimage import
ArrayInterfaceImage`.
In all such cases the relevant traceback ends with the uninformative message:
/Users/[username]/Library/Enthought/Canopy_64bit/System/lib/python2.7/site-packages/pyglet/image/__init__.py in <module>()
142
143 from pyglet import gl
--> 144 from pyglet.gl import *
145 from pyglet.gl import gl_info
146 from pyglet import graphics
/Users/[username]/Library/Enthought/Canopy_64bit/System/lib/python2.7/site-packages/pyglet/gl/__init__.py in <module>()
102 from pyglet.gl.glext_arb import *
103 from pyglet.gl.glext_missing import *
--> 104 from pyglet.gl import gl_info
105
106 import sys as _sys
ImportError: cannot import name gl_info
I am using OSX 10.6.8 on an Intel processor, with Canopy 64-bit, and these are
100% repeatable.
Given the traceback one might assume `gl_info` mistakenly isn't included, but
this isn't the case. `dir(pyglet.gl.gl_info)` can successfully be run.
## **Edit: Solved this problem.**
Pyglet 1.1.4 does not support 64-bit on OSX, so until Enthought packages a
newer release of Pyglet in Canopy, here is a workaround for 64-bit OSX users.
1. Acquire source for any release of Pyglet 1.2alpha1 or beyond.
2. Extract source to your directory of choice.
3. Append this directory to the **beginning** of your PYTHONPATH environment variable, in **both** `~/.bash_profile` (for terminal shells) and `/etc/launchd.conf` (for GUI processes) with a line similar to: `export PYTHONPATH=/Users/[username]/src/pyglet-1.2alpha1:$PYTHONPATH`
4. Run this bash command in an unrelated directory and confirm the path printed leads to your 1.2alpha1 source directory: `$ python -c "import pyglet; print pyglet.__path__[0]"`
Answer: If you don't wish to modify your bash_profile, you can simply do the
following:
1. Extract latest Pyglet source to your directory of choice and cd to that directory (it should contain a setup.py file).
2. Use Canopy's Python to install Pyglet by doing the following (on Mac 64 bit): `~/Library/Enthought/Canopy_64bit/User/bin/python setup.py install`
The location of Canopy's Python for different platforms is listed here:
<https://support.enthought.com/entries/23646538-Make-Canopy-s-Python-be-your-
default-Python-i-e-on-the-PATH->
|
Putting a pointer as a value in a method call [python]
Question: I'm trying to have a function where I can put in a list and a pointer, and
have it apply that pointer to the objects in the list to give me the object
with the lowest value of that pointer.
def GetLowest(ListObject,Value):
ObjectX=ListObject[0]
for i in ListObject:
if i.Value<=ObjectX.Value:
ObjectX=i
return ObjectX
Then I could do things like (assuming I have lists of these objects)
`GetLowest(Rectangles,Area)` and have it check the area of each rectangle. Or
maybe something more complex like `GetLowest(Backpacks,Wearer.ShoeSize)`.
I'm going to want to use this in a few places around my program. Thanks in
advance, guys!
Answer: It looks to me like you would like to use the builtin
[`min`](http://docs.python.org/3/library/functions.html#min) function. `min`
takes an iterable (e.g. a list) and returns the minumum element. You can also
give it a `key` function which is called to do the comparison.
e.g.:
smallest_rectangle = min(list_of_rectangles,key=lambda rect:rect.area)
backpack_with_small_shoes = min(backpacks,key=lambda b: b.wearer.shoe_size)
The various functions in the
[`operator`](http://docs.python.org/3/library/operator.html#operator.attrgetter)
module are really useful here too. For example, the first statement above
could be written as:
from operator import attrgetter
smallest_rectangle = min(list_of_rectangles,key=attrgetter('area'))
|
Python ImportError for strptime in spyder for windows 7
Question: I can't for the life of me figure out what is causing this very odd error.
I am running a script in python 2.7 in the spyder IDE for windows 7. It uses
datetime.datetime.strptime at one point. I can run the code once and it seems
fine (although I haven't finished debugging, so exceptions have been raised
and it hasn't completed normally yet), then if I try running it again I get
the following (end of traceback only is shown):
> File "C:\path\to\test.py", line 220, in std_imp
> self.data[key].append(dt.datetime.strptime(string_var, string_format_var))
> ImportError: Failed to import _strptime because the import lockis held by
> another thread.
I am not running multiple threads with Threading etc. The only way to get the
code to make it past this point is to completely restart the computer.
Restarting spyder won't work. Web searches haven't seemed to yield any clues
or indications of others who have had this happen.
Does anyone understand what is going on? Is this some sort of GIL problem?
What is the import lock, and why does it seem to be preventing me from
importing this method of the datetime module once I have already tried running
the code once?
Answer: The solution, as noted by mfitzp, was to include a dummy call to
datetime.datetime.strptime at the beginning of the script.
e.g.
# This is a throwaway variable to deal with a python bug
throwaway = datetime.datetime.strptime('20110101','%Y%m%d')
|
Running code with another interpreter on a Perl script
Question: [This thread](http://unix.stackexchange.com/questions/74244/hybrid-code-in-
shell-scripts-sharing-variables) discusses a way of running Python code from
within a Bash script.
Is there any way to do something similar from within a Perl script? i.e. is
there any way to **run Python code typed on a Perl script?** Note that I am
not asking about running a Python **file** from a Perl script. I am asking
about running Python code directly typed within the same file that has the
Perl script (in the same way that the other thread discussed how to run Perl
code from which a Bash script).
Example:
# /bin/perl
use 5.010
my $some_perl_variable = 'hello';
# ... BEGIN PYTHON BLOCK ...
# We are still in the same file. But we are now running Python code
import sys;
print some_perl_variable # Notice that this is a perl variable
for r in range(3):
print r
# ... END PYTHON BLOCK ...
say "We are done with the Perl script!"
say "The output of the Python block is:"
print $output"
1;
Should print:
We are done with the Perl script!
The output of the Python block is:
hello
1
2
3
We are done with the perl script
Answer: It sounds like you would be interested in the
[`Inline`](https://metacpan.org/module/Inline) module. It allows Perl to call
code in many other languages, and relies on support modules for each language.
You don't say what you want to do, but you mention Python and there is an
[`Inline::Python`](https://metacpan.org/module/Inline%3a%3aPython).
|
Python "ImportError: No module named numpy"
Question: Okay so I'm fairly new to Python, I ran the commands
sudo easy_install pip
sudo pip install numpy
Afterwards, I typed python followed by `import numpy` and got the error
`ImportError: No module named numpy`
Did I miss something? Do I need to add something to sys.path?
Answer: I solved it, I had to add a path where everything was installed to my
PYTHONPATH env variable. I don't know why the installer didn't automatically
do that.
|
how to add all array's elements to one list in python
Question: with a 2 dimension array which looks like this one:
myarray = [['jacob','mary'],['jack','white'],['fantasy','clothes'],['heat','abc'],['edf','fgc']]
every elements is an array which has fixed length elements. how to become this
one,
mylist = ['jacob','mary','jack','white','fantasy','clothes','heat','abc','edf','fgc']
here's my solve
mylist = []
for x in myarray:
mylist.extend(x)
should be more simple i guess
Answer: Use `itertools.chain.from_iterable`:
from itertools import chain
mylist = list(chain.from_iterable(myarray))
Demo:
>>> from itertools import chain
>>> myarray = [['jacob','mary'],['jack','white'],['fantasy','clothes'],['heat','abc'],['edf','fgc']]
>>> list(chain.from_iterable(myarray))
['jacob', 'mary', 'jack', 'white', 'fantasy', 'clothes', 'heat', 'abc', 'edf', 'fgc']
However, [Haidro's `sum()` solution](http://stackoverflow.com/a/16316703) is
faster for your shorter sample:
>>> timeit.timeit('f()', 'from __main__ import withchain as f')
2.858742465992691
>>> timeit.timeit('f()', 'from __main__ import withsum as f')
1.6423718839942012
>>> timeit.timeit('f()', 'from __main__ import withlistcomp as f')
2.0854451240156777
but `itertools.chain` wins if the input gets larger:
>>> myarray *= 100
>>> timeit.timeit('f()', 'from __main__ import withchain as f', number=25000)
1.6583486960153095
>>> timeit.timeit('f()', 'from __main__ import withsum as f', number=25000)
23.100156371016055
>>> timeit.timeit('f()', 'from __main__ import withlistcomp as f', number=25000)
2.093297885992797
|
savetxt two columns in python,numpy
Question: I have some data as numpy 2D array list-
array([[ 0.62367947],
[ 0.95427859],
[ 0.97984112],
[ 0.7025228 ],
[ 0.86436385],
[ 0.71010739],
[ 0.98748138],
[ 0.75198057]])
array([[-1., 1., -1.],
[-1., 1., 1.],
[ 1., 1., 1.],
[ 1., -1., 1.],
[-1., -1., -1.],
[ 1., 1., -1.],
[ 1., -1., -1.],
[-1., -1., 1.]])
And I want to save them in a txt file so that they look like
0.62367947 -1 1 -1
0.95427859 -1 1 1
0.97984112 1 1 1
Can someone help me how I can do it using numpy savetxt
Answer:
import numpy as np
R = np.array([[0.62367947],
[0.95427859],
[0.97984112],
[0.7025228],
[0.86436385],
[0.71010739],
[0.98748138],
[0.75198057]])
phase = np.array([[-1., 1., -1.],
[-1., 1., 1.],
[1., 1., 1.],
[1., -1., 1.],
[-1., -1., -1.],
[1., 1., -1.],
[1., -1., -1.],
[-1., -1., 1.]])
np.savetxt('R2.txt', np.hstack([R, phase]), fmt=['%0.8f','%g','%g','%g'])
yields
0.62367947 -1 1 -1
0.95427859 -1 1 1
0.97984112 1 1 1
0.70252280 1 -1 1
0.86436385 -1 -1 -1
0.71010739 1 1 -1
0.98748138 1 -1 -1
0.75198057 -1 -1 1
* * *
[np.hstack](http://docs.scipy.org/doc/numpy/reference/generated/numpy.hstack.html)
stacks arrays horizontally. Since `R` and `phase` are both 2-dimensional,
`np.hstack([R, phase])` yields
In [137]: np.hstack([R,phase])
Out[137]:
array([[ 0.62367947, -1. , 1. , -1. ],
[ 0.95427859, -1. , 1. , 1. ],
[ 0.97984112, 1. , 1. , 1. ],
[ 0.7025228 , 1. , -1. , 1. ],
[ 0.86436385, -1. , -1. , -1. ],
[ 0.71010739, 1. , 1. , -1. ],
[ 0.98748138, 1. , -1. , -1. ],
[ 0.75198057, -1. , -1. , 1. ]])
Passing this 2D array to `np.savetxt` gives you the desired result.
|
Make vim highlight python builtins when they are not followed by a dot
Question: Is there a way to highlight built in Python functions in vim _only_ when they
are preceded by 1 more whitespaces? Furthermore, is there a modular way to do
this? That is, I don't want to edit every single `syn keyword
pythonBuiltinFunc abs chr ...` line, I just want to be able to say something
like `syn keyword pythonBuiltinFunc onlymatchafter="\s+"`?
EDIT:
Here's an example, since the two people who answered my question didn't seem
to understand what I was asking which is my fault for not being more clear.
When I write the following Python code
import numpy as np
x = np.abs(np.random.randn(10, 10))
The word `abs` gets highlighted simply because vim is essentially just
matching anything that has the word `abs` in it that is not inside of a
string. How can I get vim to highlight the Python builtins WITHOUT
highlighting them when they are preceded by a dot?
Answer: The matched text of `:syn keyword` can only be comprised of _keyword
characters_ ; though that set can be configured (`:setlocal iskeyword=...`),
it would be foolish to include whitespace in there.
You have two options: Either re-write all keywords with `:syn match` (which
can include whitespace), or make all keywords `contained` and define a `:syn
region` that only starts after whitespace.
Both are rather huge interventions that basically mean you're (re-)writing
your own Python syntax. You haven't told us **why** you'd want that... I'd say
it's a bad idea.
|
can't concatenate strings in Python-3
Question: when running this script in Python-3:
#!/usr/bin/python
# -*- coding: utf-8 -*-
import socket
import random
import os
import threading
import sys
class bot(threading.Thread):
def __init__( self, net, port, user, nick, start_chan ):
self.id= random.randint(0,1000)
self.irc = socket.socket ( socket.AF_INET, socket.SOCK_STREAM )
self.irc_connect ( net, port )
self.irc_set_user( user,nick )
self.irc_join( start_chan )
self.finnish=False
threading.Thread.__init__(self)
def run( self ):
while not self.finnish:
serv_data_rec = self.irc.recv ( 4096 )
if serv_data_rec.find ( "PING" ) != -1:
self.irc.send( "PONG"+ serv_data_rec.split() [ 1 ] + "\r\n" )
elif serv_data_rec.find("PRIVMSG")!= -1:
line = serv_data_rec.split( "!" ) [ 0 ] + " :" + serv_data_rec.split( ":" ) [ 2 ]
self.irc_log( line )
self.irc_message( line )
def stop( self ):
self.finnish = True
self.irc_quit()
def irc_connect( self, net, port ):
self.net = net
self.port = port
self.irc.connect ( ( net, port ) )
def irc_set_user( self, user, nick ):
self.user = user
self.nick = nick
self.irc.send( "NICK " + nick + "\r\n" )
self.irc.send( "USER " + user + "\r\n" )
def irc_join( self, chan ):
self.chan = chan
self.irc.send( "JOIN " + chan + "\r\n" )
def irc_message( self, msg ):
self.irc.send( "PRIVMSG " + self.chan+" " + msg + " \r\n" )
def irc_message_nick( self, msg , nick):
self.irc.send( "PRIVMSG " + self.chan+" " + nick + " " + msg + " \r\n" )
def irc_ping( self ):
self.irc.send("PING :" + self.net)
def irc_log( self, line ):
if not os.path.exists("./logs"):
os.makedirs("./logs")
f = open("./logs/" + self.net + self.chan + "#" + "% s" %self.id,'a')
try:
f.write( line )
finally:
f.close()
def irc_quit( self ):
self.irc.send( "QUIT\r\n" )
def irc_quit_msg(self, msg):
self.irc.send( "QUIT :" + msg + "\r\n" )
def main():
bot_main= bot( "irc.freenode.net",6667,"botty botty botty :Python IRC","hello_nick","#martin3333" )
bot_main.start()
while 1:
inp = raw_input()
if inp =="!QUIT":
bot_main.stop()
break
sys.exit(0)
if __name__ == '__main__': main()
I get the following traceback:
File "./hatebozzer.py", line 84, in <module>
if __name__ == '__main__': main()
File "./hatebozzer.py", line 75, in main
bot_main= bot( "irc.freenode.net",6667,"botty botty botty :Python IRC","hello_nick","#martin3333" )
File "./hatebozzer.py", line 14, in __init__
self.irc_set_user( user,nick )
File "./hatebozzer.py", line 43, in irc_set_user
self.irc.send( "NICK " + nick + "\r\n" )
TypeError: 'str' does not support the buffer interface
I know that strings are treated completly differently in Python 3, but I am
not trying to convert strings or do anything exotic. I just want to
concatenate them, so what did I wrong here?
Answer: `send` wants a sequence of `bytes` as its argument.
In Python2, `"NICK " + nick + "\r\n"` is a sequence of bytes. But in Python3,
it is a `str`, which in Python2 would have been called a `unicode`. In Python3
this is not a sequence of bytes.
In Python3, to convert the `str` to a sequence of bytes, apply an encoding:
("NICK " + nick + "\r\n").encode('utf-8')
or (to follow best practices, use `format` instead of `+`):
"NICK {n}\r\n".format(n=nick).encode('utf-8')
|
Add sub-elements to newly created elements in python elementtree
Question: I am trying to add the following subtree to an element 'Drugs' in an xml file
using elementtree in Python based on the data in CSV file:
<Drug>
<DrugID>1<DrugID>
<Dose>40</Dose>
<Unit>mg</Unit>
</Drug>
<Drug>
<DrugID>3<DrugID>
<Dose>1</Dose>
<Unit>g</Unit>
</Drug>
The thing is once I have created the Drug element, how do I reference it to
use the append function? `element.append()` as I understand it needs element
to be a direct reference to the parent. If I use `.find()` when adding the
second drug, I may instead get a reference to the first drug.
I am cycling through each line of CSV while doing this so that's why I'd
rather add element by element rather than appending a subtree to the element
Drugs.
Answer: Use the [`SubElement`
factory](http://docs.python.org/2/library/xml.etree.elementtree.html#building-
xml-documents) to add new elements, it's much easier to use:
from xml.etree import ElementTree as ET
# drugs is a reference to your <Drugs> element
for row in csvreader:
drug = ET.SubElement(drugs, 'Drug')
ET.SubElement(drug, 'DrugID').text = row[0]
ET.SubElement(drug, 'Dose').text = row[1]
ET.SubElement(drug, 'Unit').text = row[2]
where I assume that the columns 1 - 3 are the drug id, dose and unit, adjust
as required for your CSV file.
Calling `SubElement()` creates the element, adds it to the parent and returns
the newly created element for further processing.
|
Invisible button (using pack_forget) still occupies space
Question: I use pack_forget() to make a button invisible. But when i subsequently create
a label, it appears bellow the invisible button. How can i avoid this
displacement?
The following sample code demonstrates the issue:
from tkinter import *
class Application(Frame):
def secondwidget(self):
self.b.pack_forget()
self.l = Label(text="Lowered Label :(")
self.l.pack()
def firstwidget(self):
self.b = Button(self)
self.b["text"] = "Button"
self.b["command"] = self.secondwidget
self.b.pack()
def __init__(self, master=None):
Frame.__init__(self, master)
self.pack()
self.firstwidget()
root = Tk()
app = Application(master=root)
app.mainloop()
root.destroy()
EDIT: I use python 3.2
Answer: You forgot to set parent for label:
self.l = Label(text="Lowered Label :(")
print(self.l.winfo_parent() == str(self))
>>> False
Compare:
self.b = Button(self)
print(self.b.winfo_parent() == str(self))
>>> True
|
Executable Python Zip with C extensions
Question: I have a zip file with a `__main__.py` that executes fine: ./myapp
But inside of this zip, there is a C extension library.so file that must be
loaded but this library.so file is not being found.
If I execute the directory (without zipping it), it executes correctly. So it
appears the C extensions are not supported or is some configuration issue. Any
ideas?
<http://www.python.org/dev/peps/pep-0441/>
Answer: C extensions cannot be loaded from `.zip` libraries. This is a limitation
outside of Python's control.
This already applied to [`zipimport`
support](http://docs.python.org/2/library/zipimport.html):
> Any files may be present in the ZIP archive, but only files .py and .py[co]
> are available for import. ZIP import of dynamic modules (.pyd, .so) is
> disallowed.
|
Python numpy loadtxt fails with date time
Question: I am trying to use numpy loadtxt to load a csv file into an array. But it seem
i can't get the date time correctly loaded.
Below demonstrates what is happening. Did I do something wrong?
>>> s = StringIO("05/21/2007,03:27")
>>> np.loadtxt(s, delimiter=",", dtype={'names':('date','time'), 'formats':('datetime64[D]', 'datetime64[m]')})
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/numpy/lib/npyio.py", line 796, in loadtxt
items = [conv(val) for (conv, val) in zip(converters, vals)]
File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/numpy/lib/npyio.py", line 573, in <lambda>
return lambda x: int(float(x))
ValueError: invalid literal for float(): 05/21/2007
Answer: Trying MichealJCox's solution did not work for me. My version of numpy (1.8)
would not accept a time number as given by `strpdate2num('%m/%d/%Y')`, it
would only accept a date string or datetime object. Therefore, I used a more
complex converter, which converts the time string to a time number and then to
a datetime object usable by numpy :
from matplotlib.dates import strpdate2num, num2date
...
convert = lambda x: num2date(strpdate2num('%m/%d/%Y')(x))
np.loadtxt(s, delimiter=",", converters={0:convert}, dtype= ...
This seems like a bulky solution though.
|
Using variables declared in functions and use them in another function in a different class
Question:
#!/usr/bin/python
import MainPanel
import wx
########################################################################
class OtherFrame(wx.Frame):##open PDB frame
""""""
#----------------------------------------------------------------------
def __init__(self):
"""Constructor"""
wx.Frame.__init__(self, None, wx.ID_ANY, "Secondary Frame")
panel = wx.Panel(self)##create panel
chain = wx.Button(panel, label = "OK", pos=(100,80),size=(53,25))##button create
self.Bind(wx.EVT_BUTTON,self.getchain,chain)##bind event to button go to getchain method
def getchain(self,event):
global flag
flag = 1
import OtherFrame
#######
class MainPanel(wx.Panel):##main frame
""""""
#----------------------------------------------------------------------
def __init__(self, parent, size = (5000,5000)):
"""Constructor"""
wx.Panel.__init__(self, parent=parent, size = (5000,5000))
self.frame = parent
Publisher().subscribe(self.showFrame, ("show.mainframe"))
def showFrame(self, msg):
#------------------------------------------------------------------
def createfigure():
OtherF = OtherFrame.OtherFrame()
OtherF.getchain()
print flag
First of all I have shortened down my code massively due to it being over 1000
lines of code. What I am wanting to do is get the variables declared in
`getchain` and use them in the `def createfigure`. They are from different
classes. At the moment I am getting the error `getchain() takes exactly 2
arguments (1 given)` Could someone tell me where I am going wrong, and how to
get the variables I use in `def getchain(self,event)` and use them in `def
createfigure`
Answer: You shouldn't do that. If you really, really want to, then it's better to make
the variables class properties by pre-pending them with "self.". So if you
want to access the "flag" variable in the other class, make it "self.flag".
Then you can access it using OtherF.flag. However, I think if you need to get
something from another class, I recommend using pubsub to pass it around.
Here's a tutorial:
* <http://www.blog.pythonlibrary.org/2010/06/27/wxpython-and-pubsub-a-simple-tutorial/>
|
Point in convex polygon
Question: I'm trying to make a function that will return `True` if the given (x,y) point
is inside a convex polygon. I'm trying to make it without numpy or any similar
imports, just pure python code.
I've already found a sample solution, which seems OK at first sight, but it's
not working correctly, and I can't figure out why. The code is as follows:
def point_in_poly(x,y,poly):
n = len(poly)
inside = False
p1x,p1y = poly[0]
for i in range(n+1):
p2x,p2y = poly[i % n]
if y > min(p1y,p2y):
if y <= max(p1y,p2y):
if x <= max(p1x,p2x):
if p1y != p2y:
xints = (y-p1y)*(p2x-p1x)/(p2y-p1y)+p1x
if p1x == p2x or x <= xints:
inside = not inside
p1x,p1y = p2x,p2y
return inside
If I test it for (9,9), for the following polygon, it gives me `True`:
polygon = [(0,10),(10,10),(10,0),(0,0)]
point_x = 9
point_y = 9
print point_in_poly(point_x,point_y,polygon)
But when I change the order of the points of the polygon, for the same point,
it gives me `False`:
polygon = [(0,0), (0,10), (10,0), (10,10)]
point_x = 9
point_y = 9
print point_in_poly(point_x,point_y,polygon)
Anybody knows the reason? Thanks!
Answer: In the particular case you are having problems with is special: polygon =
[(0,0), (0,10), (10,0), (10,10)]
Changing the order of points in a polygon can have significant impact on
algorithms.
If you draw your polygon on a graph you'll see you have a horizontal hourglass
shape. The polygon border overlaps itself. In geospatial analysis this overlap
is not allowed because visually and logically you now have two closed polygons
with a common intersection point. By the way most geospatial software doesn't
deal well with triangles either.
In this case the point at 9,9 will trick the ray casting algorithm used in
your method above because it can easily cross the doubled-over polygon
boundary twice.
Please run the following code to see what is going on. (9,9) is on the line
and this algorithm doesn't account for it. (5,8) is way outside:
import turtle as t
polygon = [(0,0), (0,100), (100,0), (100,100)]
t.goto(0,0)
fp = None
for p in polygon:
t.goto(p)
if not fp: fp=p
t.goto(fp)
t.up()
t.goto(90,90)
t.write("90,90")
t.dot(10)
t.goto(50,80)
t.write("50,80")
t.dot(10)
t.done()
This code handles the (9,9) edge case:
[http://geospatialpython.com/2011/08/point-in-polygon-2-on-
line.html](http://i.stack.imgur.com/xYNRu.png)
|
Multiprocessing with Python and Arguements
Question: related to my last post (Which somehow got marked off and closed), I wrote
some code to create a thread for a command handler for my python TCP listener.
What basically happens is that I send in some data and it goes in the TCP
connecter. Then the TCP connector creates another process and sends the data
that it received through the process to the function in the command listener.
I do not know what is going on. Please help!
import socket
import sys
import errno
from multiprocessing import Process, Queue # @UnresolvedImport
import CommandHandler
class tcpconnection:
def tcp(self):
data = ''
q = Queue()
p = Process(target=CommandHandler.CommandHandler.commands(), args=(self, data))
#
HOST = '' # Symbolic name meaning all available interfaces
PORT = 9999 # Arbitrary non-privileged port
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((HOST, PORT))
s.listen(1)
conn, addr = s.accept()
print('Connected by', addr)
while True:
data = conn.recv(1024)
p.start()
p.join()
if not data: break
conn.send(data)
conn.close()
Says that:
p = Process(target=CommandHandler.CommandHandler.commands(), args=(self, data))
TypeError: unbound method commands() must be called with CommandHandler instance as first argument (got nothing instead)
Answer: `target=CommandHandler.CommandHandler.commands()` sets the `target` argument
to the result of the invocation of the `commands` method. What you probably
intended to do was to use that method as tharget, so you should use:
p = Process(target=CommandHandler.CommandHandler.commands, args=(self, data))
Also the error tells you that you're trying to call an unbound method on a
class, but you need an object to call it on, probably:
p = Process(target=CommandHandler.CommandHandler().commands, args=(self, data))
but that's not your only issue:
while True:
data = conn.recv(1024)
p.start()
p.join()
This loop will fail after the first invocation, because you can't restart an
already started process.
|
Searching for books with the Amazon Product Advertising API - Python
Question: tl;dr : I am using the Amazon Product Advertising API with Python. How can I
do a keyword search for a book and get XML results that contain TITLE, ISBN,
and PRICE for each entry?
Verbose version:
I am working in Python on a web site that allows the user to search for
textbooks from different sites such as eBay and Amazon. Basically, I need to
obtain simple information such as titles, ISBNS, and prices for each item from
a set of search results from one of those sites. Then, I can store and format
that information as needed in my application (e.g, displaying HTML).
In eBay's case, getting the info I needed wasn't too hard. I used `urllib2` to
make a request based on a sample I found. All I needed was a special security
key to add to the URL:
def ebaySearch(keywords): #keywords is a list of strings, e.g. ['moby', 'dick']
#findItemsAdvanced allows category filter -- 267 is books
#Of course, I replaced my security appname in the example below
url = "http://svcs.ebay.com/services/search/FindingService/v1?OPERATION-NAME=findItemsAdvanced&SERVICE-NAME=FindingService&SERVICE-VERSION=1.0.0&SECURITY-APPNAME=[MY-APPNAME]&RESPONSE-DATA-FORMAT=XML&REST-PAYLOAD&categoryId=267&keywords="
#Complete the url...
numKeywords = len(keywords)
for k in range(0, numKeywords-1):
url += keywords[k]
url += "%20"
#There should not be %20 after last keyword
url += keywords[numKeywords-1]
request = urllib2.Request(url)
response = urllib2.urlopen(request) #file like thing (due to library conversion)
xml_response = response.read()
...
...Then I parsed this with minidom.
In Amazon's case, it doesn't seem to be so easy. I thought I would start out
by just looking for an easy wrapper. But their developer site doesn't seem to
provide a python wrapper for what I am interested in (the Product Advertising
API). One that I have tried, python-amazon-product-api 0.2.5 from
<https://pypi.python.org/pypi/python-amazon-product-api/>, has been giving me
some installation issues that may not be worth the time to look into (but
maybe I'm just exasperated..). I also looked around and found pyaws and pyecs,
but these seem to use deprecated authentication mechanisms.
I then figured I would just try to construct the URLs from scratch as I did
for eBay. But Amazon requires a time stamp in the URLs, which I suppose I
could programatically construct (perhaps something like these folks, who go
the whole 9 yards with the signature:
<https://forums.aws.amazon.com/thread.jspa?threadID=10048>).
Even if that worked (which I doubt will happen, given the amount of
frustration the logistics have given so far), the bottom line is that I want
name, price, and ISBN for the books that I search for. I was able to generate
a sample URL with the tutorial on the API website, and then see the XML
result, which indeed contained titles and ISBNs. But no prices! Gah! After
some desperate Google searching, a slight modification to the URL (adding
&ResponseGroup=Offers and &MerchantID=All) did the trick, but then there were
no titles. (I guess yet another question I would have, then, is where can I
find an index of the possible ResponseGroup parameters?)
Overall, as you can see, I really just don't have a solid methodology for
this. Is the construct-a-url approach a decent way to go, or will it be more
trouble than it is worth? Perhaps the tl;dr at the top is a better
representation of the overall question.
Answer: Another way could be [amazon-simple-product-
api](https://github.com/yoavaviram/python-amazon-simple-product-api):
from amazon.api import AmazonAPI
amazon = AmazonAPI(ACCESS_KEY, SECRET, ASSOC)
results = amazon.search(Keywords = "book name", SearchIndex = "Books")
for item in results:
print item.title, item.isbn, item.price_and_currency
To install, just clone from github and run
sudo python setup.py install
Hope this helps!
|
querying data from sqlalchemy database
Question:
engine = create_engine('sqlite:///nwtopology.db', echo=False)
Base = declarative_base()
class SourcetoPort(Base):
""""""
__tablename__ = 'source_to_port'
id = Column(Integer, primary_key=True)
port_no = Column(Integer)
src_address = Column(String)
#----------------------------------------------------------------------
def __init__(self, src_address,port_no):
""""""
self.src_address = src_address
self.port_no = port_no
Session = sessionmaker(bind=engine)
session = Session()
self.mac_to_port[packet.src]=packet_in.in_port
if(self.matrix.get((packet.src,packet.dst))==None):
self.matrix[(packet.src,packet.dst)]=0
print "found a new flow"
#create an databse entry with address and port
entry = SourcetoPort(src_address=str(packet.src) , port_no=packet_in.in_port)
#add the record to the session object
session.add(entry)
#add the record to the session object
session.commit()
self.matrix[(packet.src,packet.dst)]+=1
print "incrementing flow count"
#if self.mac_to_port.get(packet.dst)!=None:
if session.query(SourcetoPort).filter_by(src_address=str(packet.dst)).count():
#do stuff if the flow information is already in the databaase.
I am very new to python and sql alchemy and stuff.the above code is releavnt
portions of a network controller.The above piece of code gets called whenever
a new packet comes in.My question is
if session.query(SourcetoPort).filter_by(src_address=str(packet.dst)).count():
is this the correct/most efficient way to know if the src_address is already
in the databse.?Can someone suggest some better method.relying on positive
count doesn't seem too rigid.
Answer: Couple suggestions
1) make sure that your table has index created on src_address field. If you
are using SQLAlchemy to create schema index can be added with this simple
change to table definition. (see more at [Describing Databases with MetaData:
Indexes part of SQLAlchemy
manual](http://docs.sqlalchemy.org/en/rel_0_8/core/schema.html?highlight=index#indexes))
class SourcetoPort(Base):
""""""
__tablename__ = 'source_to_port'
id = Column(Integer, primary_key=True)
port_no = Column(Integer)
src_address = Column(String, index=True)
2) To check if there any records with src_address=str(packet.dst) there is
another way by using EXISTS. So it won't have to scan all records what has
such src_address but return results as soon as it finds first records with
such field value.
if session.query(SourcetoPort).filter_by(src_address=str(packet.dst)).count():
#do stuff if the flow information is already in the databaase.
Replace count query with exists query
from sqlalchemy.sql.expression import exists
if session.query(exists().where(SourcetoPort.src_address == '123')).scalar() is not None:
#do stuff if the flow information is already in the database.
3) I'm not sure what task your are solving by programming this script. I just
hope you are not going to start new python script every time new network
packet arrives to network interface. Starting new python interpreter process
takes seconds and there can be thousands of packets per second arriving. In
the latter case I would consider running such network controller program as a
daemon and would cache all information in memory. Also I would implement
database operations to run asynchronously in separate thread or even thread
pool, so they won't block main thread controlling network flow.
|
Registration Form import error
Question: I am following DjangoBook tutorial and i have encountered a problem on chapter
14 ( User Registration )
In _django.contrib.auth.forms_ , there is a `UserCreationForm` class. I am
trying to create a new class based on `UserCreationForm` called `RegisterForm`
This is my class `RegisterForm` in _django.contrib.auth.forms_
class RegisterForm(UserCreationForm):
email = forms.EmailField(label="Email")
fullname = forms.CharField(label="Full name")
class Meta:
model= User
fields = ("username","fullname","email",)
This is the view function
def register(request):
if request.method == 'POST':
form = UserCreationForm(request.POST)
if form.is_valid():
new_user = form.save()
return HttpResponseRedirect("/books/")
else:
form = RegisterForm(UserCreationForm)
return render(request, "registration/register.html", {
'form': form,
})
I have no idea why i am getting a ImportError which states that I cannot
import name `RegisterForm` in my view , can someone help me out thanks.
This is my stack trace
Environment:
Request Method: GET
Request URL: http://127.0.0.1:8000/register/
Django Version: 1.5.1
Python Version: 2.7.2
Installed Applications:
('django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.staticfiles',
'django.contrib.admin',
'mysite.books')
Installed Middleware:
('django.middleware.common.CommonMiddleware',
'django.contrib.sessions.middleware.SessionMiddleware',
'django.middleware.csrf.CsrfViewMiddleware',
'django.contrib.auth.middleware.AuthenticationMiddleware',
'django.contrib.messages.middleware.MessageMiddleware')
Traceback:
File "C:\Python27\lib\site-packages\django\core\handlers\base.py" in get_response
103. resolver_match = resolver.resolve(request.path_info)
File "C:\Python27\lib\site-packages\django\core\urlresolvers.py" in resolve
319. for pattern in self.url_patterns:
File "C:\Python27\lib\site-packages\django\core\urlresolvers.py" in url_patterns
347. patterns = getattr(self.urlconf_module, "urlpatterns", self.urlconf_module)
File "C:\Python27\lib\site-packages\django\core\urlresolvers.py" in urlconf_module
342. self._urlconf_module = import_module(self.urlconf_name)
File "C:\Python27\lib\site-packages\django\utils\importlib.py" in import_module
35. __import__(name)
File "C:\Users\Ray Lim\Desktop\project\home\username\djcode\mysite\mysite\urls.py" in <module>
14. from mysite.books import views
File "C:\Users\Ray Lim\Desktop\project\home\username\djcode\mysite\mysite\books\views.py" in <module>
11. from django.contrib.auth.forms import RegisterForm
Exception Type: ImportError at /register/
Exception Value: cannot import name RegisterForm
Answer: As of **Django 1.5** there is no such form in the module
`django.contrib.auth.forms.`
You might want to use an editor that would highlight such things for you. Such
as [PyCharm](https://www.jetbrains.com/pycharm/).
Still, point stands, you should have at least basic understanding of `Python`
to learn `Django`. You see, the statements
class RegisterForm(UserCreationForm)
...
# And then:
form = RegisterForm(UserCreationForm)
Hardly make any sense from Python perspective.
You are writing Python code. In Python. You'll have to learn Python. Yes, it
is possible to go another way, but it is much harder.
|
Synchronizing Plone 4 sites
Question: I'm using Plone 4 for my sites and I was wondering if there is a way to
synchronize two plone sites i.e. be able to synchronize my development site
with my production site.
I have looked at [Zsyncer](https://pypi.python.org/pypi/Products.ZSyncer)
product and it appears it is no longer maintained. Besides, the last version
is not compatible with Plone 4.
I am thinking of writing a custom script that will handle exporting of the
data.fs files and the src files as explained in these two articles:
[Copying a remote site
database](http://developer.plone.org/hosting/zope.html#copying-a-remote-site-
database)
[Copying a Plone site](http://plone.org/documentation/kb/copying-a-plone-site)
Is there a better way of synchronizing two plone sites as described by my use
case above?
Answer: For keeping the code synchronized, you want collective.hostout
For the database, use collective.recipe.backup - you could probably also use
hostout to import the backups
|
Global name in Python
Question: I want to find out whether two numbers **N1** and **N2** are the permutations
of the same digits. For example `123` and `321` are permutations of the same
digits, where as `234` and `123` are not. I have used Python to solve the
problem of which I am not an expert. I am using `IDLE Python GUI` on `Windows
7`. The specifications are `Python 2.7.3 (default, Apr 10 2012, 23:31:26) [MSC
v.1500 32 bit (Intel)] on win32`.
The Python code is shown below,
def k(n, m):
s1 = n
s2 = m
k = 0
fl = 0
while k < 10 :
arr1[k] = 0
arr2[k] = 0
k = k + 1
while s1 > 0 :
t = s1 % 10
arr1[t] = 1
t = s2 % 10
arr2[t] = 1
s1 = s1 / 10
s2 = s2 / 10
k = 0
while k < 10 :
if arr1[k] != arr2[k]:
fl = 1
k = k + 1
return fl
I saved the file as `k.py` and imported using the following command `import
k`. But when I tried to execute the code as `k.k(123, 321)` I am getting the
following error.
Traceback (most recent call last):
File "<pyshell#7>", line 1, in <module>
k.k(123,321)
File "k.py", line 7, in k
global arr2
NameError: global name 'arr1' is not defined
I tried to declare the arrays as follows,
arr1 = []
arr2 = []
I also tried,
global arr1 = []
global arr2 = []
and
global arr1
global arr2
But I am still getting the same error. What is wrong with my code?
I have checked the following answers in **SO** but I couldn't solve my
problem.
[Help Defining Global Names](http://stackoverflow.com/questions/3595690/help-
defining-global-names)
[use of "global" keyword in
python](http://stackoverflow.com/questions/4693120/use-of-global-keyword-in-
python)
**What I believed was that in Python you don't have to declare any variables,
instead you can simply use them. Am I wrong about this assumption?**
Any suggestions? Thank you.
Answer: There is no need to do anything with global values here. Everything should be
contained within the function.
The problem is simply that you don't define `arr1` or `arr2` before you try
appending to them. You need to define them _in that function_ , along with
`s1`, `s2`, `k` and `fl`.
**Edit** I should add that your code is extremely unPythonic. All these while
loops with incrementing counters should be replaced with for loops: `for k in
range(10)` etc. But the first loop isn't even necessary - you should have
`arr1 = [0] * 10` and the same for `arr2`.
|
how to disable the automatic mapping of std::vector<std::vector<double> > to tuple of tuples in swig python?
Question: Apparently, swig transform automatically `std::vector<std::vector<double> >`
to a tuple of tuples. I want to prevent this, and I want the type to be kept
as is. How can I achieve it? I tried specifying a definition for the type
%template(StdVectorStdVectorDouble) std::vector<std::vector<double> >;
but apparently it does not work.
Answer: Two techniques:
1. `%clear` the typemap for the type before the function is processed by SWIG.
2. Declare the `%template` _after_ the function is processed by SWIG.
### Example 1
%module x
%begin %{
#pragma warning(disable:4127 4211 4701 4706)
%}
%include <std_vector.i>
%template(vd) std::vector<double>;
%template(vvd) std::vector<std::vector<double> >;
%clear std::vector<std::vector<double> >;
%inline %{
#include<vector>
std::vector<std::vector<double> > func()
{
std::vector<std::vector<double> > temp;
std::vector<double> a;
a.push_back(1.5);
temp.push_back(a);
return temp;
}
%}
### Example 2
%module x
%begin %{
#pragma warning(disable:4127 4211 4701 4706)
%}
%include <std_vector.i>
%inline %{
#include<vector>
std::vector<std::vector<double> > func()
{
std::vector<std::vector<double> > temp;
std::vector<double> a;
a.push_back(1.5);
temp.push_back(a);
return temp;
}
%}
%template(vd) std::vector<double>;
%template(vvd) std::vector<std::vector<double> >;
### Result (of both)
Python 3.3.0 (v3.3.0:bd8afb90ebf2, Sep 29 2012, 10:57:17) [MSC v.1600 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import x
>>> x.func()
<x.vvd; proxy of <Swig Object of type 'std::vector< std::vector< double,std::allocator<double > > > *' at 0x00000000025F6900> >
|
Importing the `this` module?
Question: Typing the following in a a Python shell does not produce an error:
from this import *
What is the `this` module?
Answer: `this` is the [`zen of python`](http://www.python.org/dev/peps/pep-0020/)
written by Tim Peters
>>> from this import *
The Zen of Python, by Tim Peters
Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested.
Sparse is better than dense.
Readability counts.
.....
>>> d
{'A': 'N', 'C': 'P', 'B': 'O', 'E': 'R', 'D': 'Q', 'G': 'T', 'F': 'S', 'I': 'V', 'H': 'U', 'K': 'X', 'J': 'W', 'M': 'Z', 'L': 'Y', 'O': 'B', 'N': 'A', 'Q': 'D', 'P': 'C', 'S': 'F', 'R': 'E', 'U': 'H', 'T': 'G', 'W': 'J', 'V': 'I', 'Y': 'L', 'X': 'K', 'Z': 'M', 'a': 'n', 'c': 'p', 'b': 'o', 'e': 'r', 'd': 'q', 'g': 't', 'f': 's', 'i': 'v', 'h': 'u', 'k': 'x', 'j': 'w', 'm': 'z', 'l': 'y', 'o': 'b', 'n': 'a', 'q': 'd', 'p': 'c', 's': 'f', 'r': 'e', 'u': 'h', 't': 'g', 'w': 'j', 'v': 'i', 'y': 'l', 'x': 'k', 'z': 'm'}
>>> c
'!'
And why would `from this import *` raise an error?
Using the above syntax simply merges `this` module's namespace into current
namespace.
>>> import this
>>> dir(this)
['__builtins__', '__doc__', '__file__', '__name__', '__package__', 'c', 'd', 'i', 's']
Also try:
import antigravity
|
Assigning a function (which is assigned dynamically) along with specific parameters, to a variable.
Question: Ok, so here's the deal, say I have a function( take_action ), that calls
another function. But we don't know which function take_action is going to
call.
I had that part figured out thanks to [this
question](http://stackoverflow.com/questions/4246000/python-calling-functions-
dynamically), the thing is, on that question they deal with functions that
take no arguments, my take_action could take one of several different
functions that are quite different from each other, with completely different
actions taken, different arguments.
Now for some example code:
def take_action():
action['action']()
#does other stuff with 'other_stuff_in_the_dic'
def move(x,y):
#stuff happens
action = {'action': move, 'other_stuff_in_the_dic': 'stuff' }
(In this case the 'action' would be move, but like I said, that's assigned
dynamically depending on certain user input)
What I would like to do, is something like this:
action = { 'action': move(2,3), 'other_stuff': 'stuff' }
(Obviously that calls the function there, since it has the (), hence it
wouldn't work)
I'm only a beginner programmer, and the only thing I thought of is using a
list, which is in another key inside the dic, but that would just pass one
list argument, instead of each content of the list being passed on as an
argument.
What would be a way to achieve this, so the 'action' key (or the dictionary on
another key?) also stores the arguments it should use when I call it on
take_action?
Answer: Use
[`functools.partial()`](http://docs.python.org/3/library/functools.html#functools.partial)
to store functions with their arguments:
from functools import partial
action = {'action': partial(move, 2, 3), 'other_stuff': 'stuff'}
Calling `action['action']()` results in `move(2, 3)` being called.
|
Take a screenshot from a website from commandline or with python
Question: i will take a screenshot from this page:
[http://books.google.de/books?id=gikDAAAAMBAJ&pg=PA1&img=1&w=2500](http://books.google.de/books?id=gikDAAAAMBAJ&pg=PA1&img=1&w=2500)
or save the image that it outputs.
But i can't find a way. With wget/curl i get an "unavailable error" and also
with others tools like webkit2png/wkhtmltoimage/wkhtmltopng.
Is there a clean way to do it with python or from commandline?
Best regards!
Answer: You can use ghost.py if you like. <http://jeanphix.me/Ghost.py/>
Here is an example of how to use it.
from ghost import Ghost
ghost = Ghost(wait_timeout=4)
ghost.open('http://www.google.com')
ghost.capture_to('screen_shot.png')
The last line saves the image in your current directory.
Hope this helps
|
Histogram in Python Using matplotlib
Question: I am struggling with this really badly. There is something that I'm just not
getting. I have a function, which I want to plot a histogram of a dictionary
with the keys on the x-axis and the values on the y-axis, then save the file
in a location specified when calling the function. What I have is:
import matplotlib.pyplot as plt
def test(filename):
dictionary = {0:1000, 1:20, 2:15, 3:0, 4:5}
xmax = max(dictionary.keys())
ymax = max(dictionary.values())
plt.hist(dictionary,xmax)
plt.title('Histogram Title')
plt.xlabel('Label')
plt.ylabel('Another Label')
plt.axis([0, xmax, 0, ymax])
plt.figure()
plt.savefig(filename)
test('test_graph.svg')
I simply cannot get this to work, and I've struggled for a very long time
reading other questions and documentation. Any help would be greatly
appreciated. Thanks.
EDIT:
The error I have is:
File "/usr/lib/pymodules/python2.7/matplotlib/pyplot.py", line 343, in figure
**kwargs)
File "/usr/lib/pymodules/python2.7/matplotlib/backends/backend_tkagg.py", line 80, in new_figure_manager
window = Tk.Tk()
File "/usr/lib/python2.7/lib-tk/Tkinter.py", line 1688, in __init__
self.tk = _tkinter.create(screenName, baseName, className, interactive, wantobjects, useTk, sync, use)
TclError: no display name and no $DISPLAY environment variable
Answer: You are getting snarled up by the state-machine interface:
import matplotlib.pyplot as plt
def test(filename):
dictionary = {0:1000, 1:20, 2:15, 3:0, 4:5}
xmax = max(dictionary.keys())
ymax = max(dictionary.values())
plt.figure() # <- makes a new figure and sets it active (add this)
plt.hist(dictionary,xmax) # <- finds the current active axes/figure and plots to it
plt.title('Histogram Title')
plt.xlabel('Label')
plt.ylabel('Another Label')
plt.axis([0, xmax, 0, ymax])
# plt.figure() # <- makes new figure and makes it active (remove this)
plt.savefig(filename) # <- saves the currently active figure (which is empty in your code)
test('test_graph.svg')
See [How can I attach a pyplot function to a figure
instance?](http://stackoverflow.com/questions/14254379/how-can-i-attach-a-
pyplot-function-to-a-figure-instance/14261698#14261698) for a longer
explanation of the state-machine vs OO interfaces for matplotlib.
|
Looking for command line ftp client (linux)
Question: I am looking to batch download a large number of files (>800). I have a text
file with the list of all the filenames. These filenames are then used to
derive the URL from which they can be downloaded. I had been parsing through
the file with a python script, using subprocess to wget the files.
wget ftp://ftp.name.of.site/filename-prefix/filename/filename+suffix
However for reasons unknown to me, wget is failing to properly connect. I
wanted to know if I could essentially use an ftp program that would work in a
similar manner, i.e. no login and stay within the commandline.
Edit: What's in my text file:
ERS032033
ERS032214
ERS032234
ERS032223
ERS032218
The ERS### act as the prefix. The whole thing is the filename. The final file
(i.e. filename+suffix) would look something like: ERS032033_1.fastq.gz
Submitting the correct url is not the problem.
Answer: Since you are using Python, I suggest dropping the subprocess approach and
using the `urllib` module instead:
import urllib
handle = urllib.urlopen('ftp://ftp.name.of.site/filename-prefix/filename/filename+suffix')
print handle.read()
handle.close()
Assuming you are using Python 2
([urllib.request](http://docs.python.org/3/library/urllib.request.html#module-
urllib.request) for Python 3)
If you simply need batch download,
[urllib.urlretrieve](http://docs.python.org/2/library/urllib.html#urllib.urlretrieve)
is a cleaner approach.
|
Using django.test.client to test app http requests, getting errors
Question: We're beginning to write unit tests for our API (created with the Django Rest
Framework). We decided to start off simple and use the built in unittest and
django.test.client classes. I've got the stub of a test written and it runs
just fine:
#!/usr/bin/env python
# -*- coding: utf-8 -*-
from __future__ import absolute_import
import unittest
# from django.test.client import Client
class TestGrowth(unittest.TestCase):
def setUp(self):
# self.client = Client()
pass
def test_numbers_3_4(self):
self.assertEqual(4, 4, True)
def test_strings_a_3(self):
self.assertEqual('andy', 'andy', True)
def suite():
suite = unittest.TestSuite()
# Add test cases to suite
suite.addTests(unittest.makeSuite(TestGrowth))
return suite
if __name__ == '__main__':
# Run test suite
unittest.TextTestRunner(verbosity=2).run(suite())
However as soon as I uncomment the line reading `from django.test.client
import Client` I get an error:
Traceback (most recent call last):
File "./AccountGrowth.py", line 8, in <module>
from django.test.client import Client
File "/home/vagrant/.virtualenvs/emmasocial/lib/python2.7/site-packages/django/test/__init__.py", line 5, in <module>
from django.test.client import Client, RequestFactory
File "/home/vagrant/.virtualenvs/emmasocial/lib/python2.7/site-packages/django/test/client.py", line 21, in <module>
from django.db import close_connection
File "/home/vagrant/.virtualenvs/emmasocial/lib/python2.7/site-packages/django/db/__init__.py", line 11, in <module>
if settings.DATABASES and DEFAULT_DB_ALIAS not in settings.DATABASES:
File "/home/vagrant/.virtualenvs/emmasocial/lib/python2.7/site-packages/django/conf/__init__.py", line 53, in __getattr__
self._setup(name)
File "/home/vagrant/.virtualenvs/emmasocial/lib/python2.7/site-packages/django/conf/__init__.py", line 46, in _setup
% (desc, ENVIRONMENT_VARIABLE))
django.core.exceptions.ImproperlyConfigured: Requested setting DATABASES, but settings are not configured.
You must either define the environment variable DJANGO_SETTINGS_MODULE or call settings.configure() before accessing settings.
We are defining DATABASES in settings.py as follows:
if "DATABASE_URL" in os.environ:
# Parse database configuration from $DATABASE_URL
DATABASES = {
'default': dj_database_url.config()
}
else:
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.mysql', # Add 'postgresql_psycopg2', 'postgresql', 'mysql', 'sqlite3' or 'oracle'.
'NAME': 'emmasocial', # Or path to database file if using sqlite3.
'USER': 'root', # Not used with sqlite3.
'PASSWORD': '', # Not used with sqlite3.
'HOST': '', # Set to empty string for localhost. Not used with sqlite3.
'PORT': '', # Set to empty string for default. Not used with sqlite3.
}
}
I'm running the tests from within the vagrant shell inside `<app>/api/tests`
with the following command `python ./AccountGrowth.py`.
Can anyone shed some light on why this is happening?
Answer: You're not running the tests via Django's test runner, which sets all that up
for you. You don't need that `if __name__ == '__main__'` block or its explicit
call to `run()`, and you should run your tests via `./manage.py test`.
|
Python function which will call a 1D vector values
Question: I have the next sequence of numbers of A array( is an array 1D )
1. -1.7654142212e-06
2. 7.0737426918e-07
3. 1.63230254789e-06
4. 1.88255344022e-06
5. 5.00966829007e-06
6. 1.88631278169e-06
7. -4.08751917695e-06
8. 9.12971786351e-07
9. 5.33615185204e-06
10. -1.01338496378e-05
are 100 values, just say that are only 10.
I need a function that will call these numbers.
EDIT
using x, x= np.linspace(0,1000,10)
I used scipy.interpolate.interp1d and its not working so good...
EDIT
the interpolation take the first and last value, and do an aproximation. In my
case the values are too small, and accuracy is important. Also, A values are
changing on each x step, enough to cause an error after few iterations.
So if our array is
A = ((-1.7654142212e-06 , ....,-1.01338496378e-05 ))`
I need a function to work like that:
EDIT
e.a. A_FUNCTION(0) = -1.7654142212e-06 ....
to call any value I want, without call the approximation of the value, (for a
specific #number of x) inside another function on the main or a second script.
Answer: why don't you just create a function that takes two inputs: an array, and
number
In [15]: A
Out[15]:
array([-4611686018427387904, -4611686018427387904, 7,
0, -4611686018427387904, 5764616295532855496,
-4611686018427387899, -4611686018427387904, 4,
1407374883553280])
In [16]: def grab_item(array,number):
....: return array[number]
....:
In [17]: grab_item(A,8)
Out[17]: 4
After the multitude of comments, here is an example of what I believe you want
through using this function:
In [24]: x = np.linspace(0,1000,100)
In [25]: grab_item(x,9)
Out[25]: 90.909090909090907
|
python csv reader, loop from the second row
Question: In python 2.7.3, how can I start the loop from the second row? e.g.
first_row = cvsreader.next();
for row in ???: #expect to begin the loop from second row
blah...blah...
Answer:
first_row = next(csvreader) # Compatible with Python 3.x (also 2.7)
for row in csvreader: # begins with second row
# ...
Testing it really works:
>>> import csv
>>> csvreader = csv.reader(['first,second', '2,a', '3,b'])
>>> header = next(csvreader)
>>> for line in csvreader:
print line
['2', 'a']
['3', 'b']
|
Certain trigonometry packages from numpy
Question: I'm writing code that solves the intersection of a few functions which involve
cos and sin and other various trig functions in python.
But I feel like importing NumPy as a whole is too much of a load on such a
small program, is there any other way to get basic trig functions and pi,
without importing as a whole or is just specifying
from numpy import cos
from numpy import sin
...
the easiest and most economical way to do this?
Answer: `sin`, `cos`, and `pi` are also in the
[`math`](http://docs.python.org/2/library/math.html) module. So just:
from math import sin, cos, pi
No numpy required.
If you're using `sin` and `cos` on numpy arrays, it's better to use the numpy
version, but otherwise, the ones from the math module are good.
|
Accessing API using Python
Question: I was trying to retrieve data from an API and i was receiving
**'set' object has no attribute 'items'**
This is my api.py and i have import it to my views
import json
import urllib
import urllib2
import pycurl
def get_resources(request, filter, endpoint, lookup):
headers = {'X-Auth-Token:%s' % request.user.token, 'Content-Type:application/json'}
data = urllib.urlencode(filter)
url = endpoint+lookup
req = urllib2.Request(url, data, headers)
response = urllib2.urlopen(req)
result = json.loads(response.read())
return result
and my views.py is like this
def indexView(request):
resources = json.dumps(get_resources(request,{}, api_endpoint, '/v2/meters'))
return HttpResponse(resources, mimetype='application/json')
I know that i was doing wrong here, I hope someone who could help me thanks.
Answer: The line:
headers = {'X-Auth-Token:%s' % request.user.token,
'Content-Type:application/json'}
defines a [`set`](http://docs.python.org/2/library/stdtypes.html#set). And it
should probably be a dictionary (which has `:` somewhere in after which
follows the value for the key before the `:`)
|
Implement nested interface of generic parent class with ironpython
Question: I wan't to implement the following C#/.Net interface with IronPython:
public static class Consumes<TMessage> where TMessage : class
{
public interface All
{
void Consume(TMessage message);
}
}
This is the python code I tried so far:
class TestMessage(object):
pass
class TestConsumer(Consumes[TestMessage].All):
def Consume(self, message):
pass
From this I get the following exception:
> TypeError: TestConsumer: cannot inhert from open generic instantiation
> MassTransit.Consumes`1+All[TMessage]. Only closed instantiations are
> supported.
A valid C# class definition to implement this interface looks following:
public class TestConsumer : Consumes<TestMessage>.All
{
public void Consume(TestMessage msg) { }
}
So is it not possible to implement this kind of in IronPython? Or am I doing
wrong?
Thank you in advance!
Answer: It looks like implementing the nested interface as
class TestConsumer(Consumes[TestMessage].All):
does not correctly bind the type parameter `TMessage` even though that would
be expected from the syntax. If the type is provided at the end ("for the
interface instead of the surrounding class") it seems to work as expected:
class TestConsumer(Consumes.All[TestMessage]):
What would also work is importing the interface `All` explicitly and use it
looking like a standalone generic interface:
from MyLib.Consumes import All
class TestConsumer(All[TestMessage]):
It does not seem obvious if this behavior is correct/defined that way or if
there is a bug in the [type
generation](https://github.com/IronLanguages/main/blob/master/Languages/IronPython/IronPython/Runtime/Types/NewTypeInfo.cs)
(besides from the "inhert"-typo) or in the way the generic parameters are
defined/bound. It looks to be also accepted to bind the parameter twice:
class PyTestConsumer(Consumes[String].All[String]):
even with different values which does not make much sense looking at it from a
.NET perspective:
class PyTestConsumer(Consumes[List[String]].All[String]):
|
Have a python file move itself
Question: I'm writing a script that emulates a unix environment with python (yes, I know
that may sound silly).
Basically I set up the "pwd" and "ls" commands before the "cd" command. Now I
need my python script to navigate itself around directories by moving itself.
I was wondering if anyone could point me in the right direction? eg.What
commands to use, etc
Note. I would prefer it if I only had to use built-in modules.
Thank You!
Answer: I am not sure I understand you properly, but if you are talking about moving
through the standard unix file system and not copying the script to different
locations, you could easily just wrap the three commands (pwd,ls,cd) as python
functions, just as you were describing.
In fact, I did this as part of the wx_py project; they aren't perfect clones,
but they work well enough. Here are the three functions:
import os
import glob
def pwd():
print os.getcwd()
def cd(path,usePrint=True):
os.chdir(os.path.expandvars(os.path.expanduser(path)))
if usePrint:
pwd()
def ls(str='*',fullpath=False):
g=glob.glob(os.path.expandvars(os.path.expanduser(str)))
if fullpath:
for i in g:
print i
else:
for i in g:
print os.path.split(i)[1]
The full file is at:
<https://github.com/davidmashburn/wx_py/blob/master/wx_py/path.py>
I'm sure others may have done a better job, so please just take these
functions as a starting point.
|
Python File append error
Question: This code works fine for me. Appends data at the end.
def writeFile(dataFile, nameFile):
fob = open(nameFile,'a+')
fob.write("%s\n"%dataFile)
fob.close()
But the problem is when I close the program and later run again I found that
all the previous data were lost. Process is started to write from the start
and there is no data in the file.
But during the run it perfectly add a line at the end of file.
I can't understand the problem. Please some one help.
NB: I am using Ubuntu-10.04 with python 2.6
Answer: There is nothing wrong with the code you posted here... I tend to agree with
other the comments that this file is probably being overwritten elsewhere in
your code.
The only suggestion I can think of to test this explicitly (if your use case
can tolerate it) is to throw in an exit() statement at the end of the function
and then open the file externally (aka in gedit) and see if the last change
took.
Alternatively to the exit, you could run the program in the terminal and
include a call to pdb at the end of this function which would interrupt the
program without killing it:
import pdb; pdb.set_trace()
You will then have to hit c to continue the program each time this runs.
If that checks out, do a search for other places this file might be getting
opened.
|
Is it possible to create a variable as a placeholder for 'current' value of a class in python?
Question: Let's say we have a class:
_NOTE: this is a dummy class only._
class C(object):
def __init__(self):
self.a = -10
self.b = 5
self.c = 2
def modify(self, **kwargs):
for keyword in kwargs:
vars(self)[keyword] = kwargs[keyword]
return(self)
And we want to use this modify method to change values in our object:
myclass = C()
myclass = myclass.modify(a=10)
But when I want to change the value based on the original one, I have to write
this:
myclass = C()
myclass = myclass.modify(a=myclass.a/10)
Or:
myclass = myclass.modify(a=abs(myclass.a))
My question is, is there a way, to create a global variable in a module, that
I can import and use it as a placeholder for current value, so I can use this
formula:
from globvars import current
myclass = C()
myclass = myclass.modify(
a=abs(current) % current ** 2,
b=current//2,
c=bool(current)
)
First I tried to a create a class, which will store the operation it is taking
and a value, and `modify()` will look first for its variable as a keyword and
then execute the function. Actually it is only working for simple situations
like: `current+10` or `current**2`. But when I realised, I want to use this
`current` for example with an `hsba(current)` (_color converter_) function,
where `current` is pointing to an object stored in an other object, I just
give up, I can't write this to every class I'm going to use..
Is there a solution for this? Maybe it's quite easy, I just can't see it :)
Thanks in advance for replies!
Answer: Your `modify` method could take the name of the attribute to modify, and a
function that takes the current value of the attribute and returns its new
computed value. Then you can do something like:
def compute_new_value(current):
new_value = abs(current) % current ** 2
return new_value
myclass = C()
myclass.modify('a', compute_new_value)
For simple cases, `lambda` makes it less verbose:
myclass.modify('a', lambda cur: cur + 4)
And your class:
class C(object):
[...]
def modify(self, attr_name, func):
cur_value = getattr(self, attr_name)
new_value = func(cur_value)
setattr(self, attr_name, new_value)
**Edit** : I may have missed something. Since you're writing `myclass =
myclass.modify...`, should the `modify` method return a _copy_ of the object ?
|
is there an ast python3 documentation? (At least for the Syntax)
Question: Im trying to work with the ast class in python. I want to get all Function
calls and their corresponding arguments.
How can I Implement that? The official Documentation on python.org is really
vague.
Also i tried implementing visit_Name and visit_Call. But that gives me more
than the names of the Call. It would be nice if there were some documentation
which attributes which nodes possesses. For example id for Name-nodes and func
for Call-nodes.
Answer: I know of no other documentation, but a lot can be learned by studying
examples, such as [this one](http://stackoverflow.com/a/1515403/190597), by
Alex Martelli. You could start by modifying it just slightly, this way:
import ast
class FuncVisit(ast.NodeVisitor):
def __init__(self):
self.calls = []
self.names = []
def generic_visit(self, node):
# Uncomment this to see the names of visited nodes
# print(type(node).__name__)
ast.NodeVisitor.generic_visit(self, node)
def visit_Name(self, node):
self.names.append(node.id)
def visit_Call(self, node):
self.names = []
ast.NodeVisitor.generic_visit(self, node)
self.calls.append(self.names)
self.names = []
def visit_keyword(self, node):
self.names.append(node.arg)
tree = ast.parse('''\
x = foo(a, b)
x += 1
bar(c=2)''')
v = FuncVisit()
v.visit(tree)
print(v.calls)
yields
[['foo', 'a', 'b'], ['bar', 'c']]
|
Unicode Disappearing in html.parser
Question: I am extracting HTML from some webpage with Unicode characters as follows:
def extract(url):
""" Adapted from Python3_Google_Search.py """
user_agent = ("Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US) "
"AppleWebKit/525.13 (KHTML, like Gecko)"
"Chrome/0.2.149.29 Safari/525.13")
request = urllib.request.Request(url)
request.add_header("User-Agent",user_agent)
response = urllib.request.urlopen(request)
html = response.read().decode("utf8")
return html
I am decoding properly as you can see. So `html` is now a unicode string. When
printing html, I can see the Unicode characters.
I am using `html.parser` to parse the HTML and subclassed it:
from html.parser import HTMLParser
class Parser(HTMLParser):
def __init__(self):
## some init stuff
#### rest of class
When parsing out the HTML using the class's `handle_data`, it appears that the
Unicode characters are removed/suddenly disappear. The docs do not mention
anything about encodings. Why does HTML Parser remove non-ascii characters,
and how can I fix such an issue?
Answer: Apparently, `html.parser` will call `handle_entityref` whenever it encounters
a non-ascii character. It passes the named character reference, and to convert
that to the unicode character, I used:
html.entities.html5[name]
Python's documentation does not mention that. I've never seen worse
documentation that Python.
|
Tkinter adding line number to text widget
Question: Trying to learn tkinter and python. I want to display line number for the Text
widget in an adjacent frame
from Tkinter import *
root = Tk()
txt = Text(root)
txt.pack(expand=YES, fill=BOTH)
frame= Frame(root, width=25)
#
frame.pack(expand=NO, fill=Y, side=LEFT)
root.mainloop()
I have seen an example on a site called unpythonic but its assumes that line
height of txt is 6 pixels.
I am trying something like this:
1) Binding Any-KeyPress event to a function that returns the line on which the
keypress occurs:
textPad.bind("<Any-KeyPress>", linenumber)
def linenumber(event=None):
line, column = textPad.index('end').split('.')
#creating line number toolbar
try:
linelabel.pack_forget()
linelabel.destroy()
lnbar.pack_forget()
lnbar.destroy()
except:
pass
lnbar = Frame(root, width=25)
for i in range(0, len(line)):
linelabel= Label(lnbar, text=i)
linelabel.pack(side=LEFT)
lnbar.pack(expand=NO, fill=X, side=LEFT)
Unfortunately this is giving some weird numbers on the frame. Is there a
simpler solution ? How to approach this.
thnks
Answer: I have a relatively foolproof solution, but it's complex and will likely be
hard to understand because it requires some knowledge of how Tkinter and the
underlying tcl/tk text widget works. I'll present it here as a complete
solution that you can use as-is because I think it illustrates a unique
approach that works quite well.
Note that this solution works no matter what font you use, and whether or not
you use different fonts on different lines, have embedded widgets, and so on.
## Importing Tkinter
Before we get started, the following code assumes tkinter is imported like
this if you're using python 3.0 or greater:
import tkinter as tk
... or this, for python 2.x:
import Tkinter as tk
## The line number widget
Let's tackle the display of the line numbers. What we want to do is use a
canvas, so that we can position the numbers precisely. We'll create a custom
class, and give it a new method named `redraw` that will redraw the line
numbers for an associated text widget. We also give it a method `attach`, for
associating a text widget with this widget.
This method takes advantage of the fact that the text widget itself can tell
us exactly where a line of text starts and ends via the `dlineinfo` method.
This can tell us precisely where to draw the line numbers on our canvas. It
also takes advantage of the fact that `dlineinfo` returns `None` if a line is
not visible, which we can use to know when to stop displaying line numbers.
class TextLineNumbers(tk.Canvas):
def __init__(self, *args, **kwargs):
tk.Canvas.__init__(self, *args, **kwargs)
self.textwidget = None
def attach(self, text_widget):
self.textwidget = text_widget
def redraw(self, *args):
'''redraw line numbers'''
self.delete("all")
i = self.textwidget.index("@0,0")
while True :
dline= self.textwidget.dlineinfo(i)
if dline is None: break
y = dline[1]
linenum = str(i).split(".")[0]
self.create_text(2,y,anchor="nw", text=linenum)
i = self.textwidget.index("%s+1line" % i)
If you associate this with a text widget and then call the `redraw` method, it
should display the line numbers just fine.
This works, but has a fatal flaw: you have to know when to call `redraw`. You
could create a binding that fires on every key press, but you also have to
fire on mouse buttons, and you have to handle the case where a user presses a
key and uses the auto-repeat function, etc. The line numbers also need to be
redrawn if the window is grown or shrunk or the user scrolls, so we fall into
a rabbit hole of trying to figure out every possible event that could cause
the numbers to change.
There is another solution, which is to have the text widget fire an event
whenever "something changes". Unfortunately, the text widget doesn't have
direct support for that. However, we can write a little Tcl code to intercept
changes to the text widget and generate an event for us. In an answer to the
question "[binding to cursor movement doesnt change INSERT
mark](http://stackoverflow.com/q/13835207/7432)" I offered a similar solution
that shows how to have a text widget call a callback whenever something
changes. This time, instead of a callback we'll generate an event since our
needs are a little different.
## A custom text class
Here is a class that creates a custom text widget that will generate a
`<<Change>>` event whenever text is inserted or deleted, or when the view is
scrolled.
class CustomText(tk.Text):
def __init__(self, *args, **kwargs):
tk.Text.__init__(self, *args, **kwargs)
self.tk.eval('''
proc widget_proxy {widget widget_command args} {
# call the real tk widget command with the real args
set result [uplevel [linsert $args 0 $widget_command]]
# generate the event for certain types of commands
if {([lindex $args 0] in {insert replace delete}) ||
([lrange $args 0 2] == {mark set insert}) ||
([lrange $args 0 1] == {xview moveto}) ||
([lrange $args 0 1] == {xview scroll}) ||
([lrange $args 0 1] == {yview moveto}) ||
([lrange $args 0 1] == {yview scroll})} {
event generate $widget <<Change>> -when tail
}
# return the result from the real widget command
return $result
}
''')
self.tk.eval('''
rename {widget} _{widget}
interp alias {{}} ::{widget} {{}} widget_proxy {widget} _{widget}
'''.format(widget=str(self)))
## Putting it all together
Finally, here is an example program which uses these two classes:
class Example(tk.Frame):
def __init__(self, *args, **kwargs):
tk.Frame.__init__(self, *args, **kwargs)
self.text = CustomText(self)
self.vsb = tk.Scrollbar(orient="vertical", command=self.text.yview)
self.text.configure(yscrollcommand=self.vsb.set)
self.text.tag_configure("bigfont", font=("Helvetica", "24", "bold"))
self.linenumbers = TextLineNumbers(self, width=30)
self.linenumbers.attach(self.text)
self.vsb.pack(side="right", fill="y")
self.linenumbers.pack(side="left", fill="y")
self.text.pack(side="right", fill="both", expand=True)
self.text.bind("<<Change>>", self._on_change)
self.text.bind("<Configure>", self._on_change)
self.text.insert("end", "one\ntwo\nthree\n")
self.text.insert("end", "four\n",("bigfont",))
self.text.insert("end", "five\n")
def _on_change(self, event):
self.linenumbers.redraw()
... and, of course, add this at the end of the file to bootstrap it:
if __name__ == "__main__":
root = tk.Tk()
Example(root).pack(side="top", fill="both", expand=True)
root.mainloop()
|
construct an unknown url from known information
Question: I'm trying to create a python script... basically...
I have a url to some site
url = "http://www.somesite.com/foo/bar/"
Files on server:
1-123j.jpg
2-123.jpg
3-123d.jpg
4-1594ss.jpg
...
...
45000-457li.jpg
I know the beginning of the filename (a number) and the file extension (.jpg),
but there is a part of the name that is unknown(some random string that I
don't know)...
How do I construct a url to "2-123.jpg" if I don't know the 123 part of the
name?
What I know...
correctURL = "http://www.somesite.com/foo/bar/2-*****.jpg"
the correct url would be:
"http://www.somesite.com/foo/bar/2-123.jpg"
Is this even possible?
Answer: Aside from mentioning that it is quite hard to guess random urls, I'll go
ahead and post an answer with some assumptions that might lead to a valid
solution. The disclaimer here is that I don't know what your possibilities are
with regard to server access and such, and hence will make several assumptions
on filename formats or directory contents and the like. If you have no server
access, then your solution doesn't really have a real answer to it, I guess.
So, here goes. First, get a list of filenames on the server:
import os
with open('filenames.txt') as f:
files = os.listdir('.') # Assuming you are in the correct dir
f.write('\n'.join(files))
This gives you all available files on the server. Generate this as often as
you want, automate it, preferably with copying it to your web server so that
you are always up to date.
Then, on your web server, do something like this:
files = open('filenames.txt').read().split('\n')
d = {}
for f in files:
s = f.split('-', 1)
d[s[0]] = s[-1]
Your dictionary now contains the key/value pairs needed to construct the
correct filename. You can do this periodically, storing the result somewhere
for faster access, or just run it whenever you need to construct an url.
The final step is to construct the url, like so:
n = 2 # The number you got somewhere
fmt = 'http://www.somesite.com/foo/bar/{}-{}'
url = fmt.format(n, d[n])
|
for loops, indexing, taking the min value of a list
Question: I have two shapefiles: of lakes and of cities. I need to find the closest city
to each lake and add the name of the city into the lake shapefile. I have:
for lake in lake_cursor:
lake_geom = lake.Shape
city_dist_list = [] #create a city dis list = a list of dist from one lake to each city
for cityID in range(0, city_length-1):
#obtaining x and y for both cities and lakes
cityX = citylist_X_Coor[cityID]
cityY = citylist_Y_Coor[cityID]
lakeX = lake_geom.centroid.X
lakeY = lake_geom.centroid.Y
#calculate distance
dist = math.sqrt((cityX-lakeX)**2 + (cityY-lakeY)**2)
#add the dist to the city dist list
city_dist_list.append(dist)
closest = min(city_dist_list)
closestID = city_dist_list.index(closest)
lake.City_Name = citylist_City_Name[closestID]
lake.X_Coor = citylist_X_Coor[closestID]
lake.Y_Coor = citylist_Y_Coor[closestID]
print closest
but I keep getting an error message starting at `lake.City_Name`. The python
shell isn't telling me what is wrong - any ideas? And how to fix it as well?
Thanks!
the traceback shows:
Traceback (most recent call last):
File "C:\Users\xxx\xxx\xxx.py", line 71, in <module>
lake.City_Name = citylist_City_Name[closestID]
File "C:\Program Files\ArcGIS\Desktop10.1\arcpy\arcpy\arcobjects\_base.py", line 35, in __setattr__
return setattr(self._arc_object, attr, ao)
RuntimeError: ERROR 999999: Error executing function.
Answer: Without seeing the rest of your code, it's hard to tell for certain, but it
sure looks from the traceback like you are trying to do an update in a
SearchCursor. A SearchCursor's rows don't have setters. Make sure you are
using an UpdateCursor, and don't forget to do a `lake_cursor.updateRow(lake)`
for each lake you update. Below is a simple example of how to use an
UpdateCursor.
import arcpy
fc = 'c:/temp/temp.shp'
rows = arcpy.UpdateCursor(fc)
for row in rows:
print row.Mapname
row.Mapname = 'Some Value'
rows.updateRow(row)
del row, rows
This example uses a regular `arcpy.UpdateCursor`. If you have ArcGIS 10.1,
then you can use an `arcpy.da.UpdateCursor`, which will run lot faster. Read
about these UpdateCursors
[here](http://resources.arcgis.com/en/help/main/10.1/index.html#//018v00000064000000)
and
[here](http://resources.arcgis.com/en/help/main/10.1/index.html#//018w00000014000000).
|
improving speed of Python module import
Question: The question of how to speed up importing of Python modules has been asked
previously ([Speeding up the python "import"
loader](http://stackoverflow.com/questions/2010255/speeding-up-the-python-
import-loader) and [Python -- Speed Up
Imports?](http://stackoverflow.com/questions/6025635/python-speed-up-imports))
but without specific examples and has not yielded accepted solutions. I will
therefore take up the issue again here, but this time with a specific example.
I have a Python script that loads a 3-D image stack from disk, smooths it, and
displays it as a movie. I call this script from the system command prompt when
I want to quickly view my data. I'm OK with the 700 ms it takes to smooth the
data as this is comparable to MATLAB. However, it takes an additional 650 ms
to import the modules. So from the user's perspective the Python code runs at
half the speed.
This is the series of modules I'm importing:
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.animation as animation
import scipy.ndimage
import scipy.signal
import sys
import os
Of course, not all modules are equally slow to import. The chief culprits are:
matplotlib.pyplot [300ms]
numpy [110ms]
scipy.signal [200ms]
I have experimented with using `from`, but this isn't any faster. Since
Matplotlib is the main culprit and it's got a reputation for slow screen
updates, I looked for alternatives. One is PyQtGraph, but that takes 550 ms to
import.
I am aware of one obvious solution, which is to call my function from an
interactive Python session rather than the system command prompt. This is fine
but it's too MATLAB-like, I'd prefer the elegance of having my function
available from the system prompt.
I'm new to Python and I'm not sure how to proceed at this point. Since I'm
new, I'd appreciate links on how to implement proposed solutions. Ideally, I'm
looking for a simple solution (aren't we all!) because the code needs to be
portable between multiple Mac and Linux machines.
Answer: you could build a simple server/client, the server running continuously making
and updating the plot, and the client just communicating the next file to
process.
I wrote a simple server/client example based on the basic example from the
`socket` module docs: <http://docs.python.org/2/library/socket.html#example>
here is server.py:
# expensive imports
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.animation as animation
import scipy.ndimage
import scipy.signal
import sys
import os
# Echo server program
import socket
HOST = '' # Symbolic name meaning all available interfaces
PORT = 50007 # Arbitrary non-privileged port
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((HOST, PORT))
s.listen(1)
while 1:
conn, addr = s.accept()
print 'Connected by', addr
data = conn.recv(1024)
if not data: break
conn.sendall("PLOTTING:" + data)
# update plot
conn.close()
and client.py:
# Echo client program
import socket
import sys
HOST = '' # The remote host
PORT = 50007 # The same port as used by the server
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((HOST, PORT))
s.sendall(sys.argv[1])
data = s.recv(1024)
s.close()
print 'Received', repr(data)
you just run the server:
python server.py
which does the imports, then the client just sends via the socket the filename
of the new file to plot:
python client.py mytextfile.txt
then the server updates the plot.
On my machine running your imports take 0.6 seconds, while running `client.py`
0.03 seconds.
|
Lookarounds in python
Question: I have a problem regarding lookarounds in Python:
>>> spacereplace = re.compile(b'(?<!\band)(?<!\bor)\s(?!or\b)(?!and\b)', re.I)
>>> q = "a b (c or d)"
>>> q = spacereplace.sub(" and ", q)
>>> q
# What is meant to happen:
'a and b and (c or d)'
# What instead happens
'a and b and (c and or and d)'
The regex is supposed to match any space which is not next to the words "and"
or "or", but this doesn't seem to be working.
Can anyone help me with this?
EDIT: In response to a commentor, I broken down the regex into multiple lines.
(?<!\band) # Looks behind the \s, matching if there isn't a word break, followed by "and", there.
(?<!\bor) # Looks behind the \s, matching if there isn't a word break, followed by "or", there.
\s # Matches a single whitespace character.
(?!or\b) # Looks after the \s, matching if there isn't the word "or", followed by a word break there.
(?!and\b) # Looks after the \s, matching if there isn't the word "and", followed by a word break there.
Answer: You presumably confused raw string modifier `r` with `b`.
>>> import re
>>> spacereplace = re.compile(r'(?<!\band)(?<!\bor)\s(?!or\b)(?!and\b)', re.I)
>>> q = "a b (c or d)"
>>> spacereplace.sub(" and ", q)
'a and b and (c or d)'
Sometimes, if regexp doesn't work, it may help to `DEBUG` it with `re.DEBUG`
flag. In this case by doing that you may notice, that word boundary `\b` is
not detected, which may give a hint where to search for mistake:
>>> spacereplace = re.compile(b'(?<!\band)(?<!\bor)\s(?!or\b)(?!and\b)', re.I | re.DEBUG)
assert_not -1
literal 8
literal 97
literal 110
literal 100
assert_not -1
literal 8
literal 111
literal 114
in
category category_space
assert_not 1
literal 111
literal 114
literal 8
assert_not 1
literal 97
literal 110
literal 100
literal 8
>>> spacereplace = re.compile(r'(?<!\band)(?<!\bor)\s(?!or\b)(?!and\b)', re.I | re.DEBUG)
assert_not -1
at at_boundary
literal 97
literal 110
literal 100
assert_not -1
at at_boundary
literal 111
literal 114
in
category category_space
assert_not 1
literal 111
literal 114
at at_boundary
assert_not 1
literal 97
literal 110
literal 100
at at_boundary
|
Scrape a Google Chart script with Scraperwiki (Python)
Question: I'm just getting into scraping with Scraperwiki in Python. Already figured out
how to scrape tables from a page, run the scraper every month and save the
results on top of each other. Pretty cool.
Now I want to [scrape this
page](http://developer.android.com/about/dashboards/index.html "this page")
with information on Android versions and run the script monthly. In
particular, I want the table for the version, codename, API and distribution.
It's not easy.
The table is called with a wrapper div. Is there any way to scrape this
information? I can't find any solution.
Plan B is to scrape the visualisation. What I eventually need, is the codename
and the percentage, so that's sufficient. This information can be found in the
HTML in a Google Chart script.
But I can't find this information with my 'souped' HTML. I have [a public
scraper over here](https://scraperwiki.com/scrapers/android_scraper/
"scraper"). You can edit it to make it work.
Can anyone explain how I can approach this problem? A working scraper with
comments on what's going on would be awesome.
Answer: As this is stored and rendered in JavaScript, the raw Python scraper is unable
to execute this code and view the visualisation or table.
ScraperWiki is great however I've always found, if you're doing a single page
each month, a python script + cron is much better and, if you need to have
this JavaScript parsing, using [Selenium](http://docs.seleniumhq.org/) and
it's [python driver](https://pypi.python.org/pypi/selenium) is a much more
powerful solution.
When you have the selenium server installed you can do _roughly_ the following
(in pseudocode)
#!/bin/env python
from selenium import webdriver
browser = webdriver.Firefox()
# Load page with all Javascript rendered in the DOM for you.
browser.get("http://developer.android.com/about/dashboards/index.html")
# Find the table
table = browser.find_element_by_xpath("/html/body/div[3]/div[2]/div/div/div[2]/div/div/table")
# Do something with the table element
# Save the data
browser.close()
Then just have a cron job running the script on the first day of the month
like so:
0 0 1 * * /path/to/python_script.py
|
Cannot import flask from project directory but works everywhere else
Question: So I have run into a funny problem when trying to use Flask, I can only run it
from ~/ (home) and not from ~/Projects/projectfolder. I'm using Python 2.7.4
installed via their homepage, virtualenv and virtualenvwrapper. Every time
it's the same:
$ mkvirtualenv project
New python executable in project/bin/python
Installing setuptools............done.
Installing pip...............done.
Then I install Flask:
$ pip install flask
[...]
Successfully installed flask Werkzeug Jinja2
Cleaning up...
Then I open Python from my home directory:
(project) $ python
>>> from flask import Flask
>>>
Then I quit and go to my project folder:
(project) $ cd ~/Projects/example
(project) $ python
>>> from flask import Flask
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "flask.py", line 1, in <module>
from flask import Flask
ImportError: cannot import name Flask
And I'm a bit lost as to why this is happening, anybody have any ideas?
Answer: According to you traceback, you have a module of your own called `flask.py` in
`~/Projects/example`.
The current directory is searched before the actual package installation path,
so it shadows the "real" Flask.
|
how to access a nested comprehensioned-list
Question: I have a working solution for creating a list some of random numbers, count
their occurrencies, and put the result in a dictionary which looks the
following:
random_ints = [random.randint(0,4) for _ in range(6)]
dic = {x:random_ints.count(x) for x in set(random_ints)])
so that for, say [0,2,1,2,1,4] I get {0: 1, 1: 2, 2: 2, 4:1}
I was wondering if its possible to express this in a one liner, preferably
without the use of a library function - I want to see what's possible with
python :) When I try to integrate the two lines in one I dont know howto
express the two references to the same comprehensioned list of random_ints
..??? I expected something like:
dic = {x:random_ints.count(x) for x in set([random.randint(0,4) for _ in range(6)] as random_ints))
which of course does not work...
I looked (nested) list comprehensions up here on SO, but I could not apply the
solutions I found to my problem.
thanks, s.
Answer: Here is a one-liner that relies on `random` and `collections` modules.
>>> import collections
>>> import random
>>> c = collections.Counter(random.randint(0, 6) for _ in range(100))
>>> c
Counter({2: 17, 1: 16, 0: 14, 3: 14, 4: 14, 5: 13, 6: 12})
|
How to make each tweet on its own line?
Question: I am wanting to have each tweet be on its own line.
Currently, this breaks at each response (I listed Response_1...I am using
through Response_10)
Any ideas?
#!/usr/bin/env python
import urllib
import json
response_1 = urllib.urlopen("http://search.twitter.com/search.json?q=microsoft&page=1")
for i in response_1:
print (i, "\n")
Answer: You have to parse the json as a python object first, only then you can iterate
over it.
#!/usr/bin/env python
import urllib
import json
response_1 = json.loads(urllib.urlopen("http://search.twitter.com/search.json?q=microsoft&page=1").read())
for i in response_1['results']:
print (i, "\n")
|
Python: Number ranges that are extremely large?
Question:
val = long(raw_input("Please enter the maximum value of the range:")) + 1
start_time = time.time()
numbers = range(0, val)
shuffle(numbers)
I cannot find a simple way to make this work with extremely large inputs - can
anyone help?
I saw a question like this - but I could not implement the range function they
described in a way that works with shuffle. Thanks.
Answer: To get a random permutation of the range `[0, n)` in a memory efficient
manner; you could use
[`numpy.random.permutation()`](http://docs.scipy.org/doc/numpy/reference/generated/numpy.random.permutation.html#numpy.random.permutation):
import numpy as np
numbers = np.random.permutation(n)
If you need only small fraction of values from the range e.g., to get `k`
random values from `[0, n)` range:
import random
from functools import partial
def sample(n, k):
# assume n is much larger than k
randbelow = partial(random.randrange, n)
# from random.py
result = [None] * k
selected = set()
selected_add = selected.add
for i in range(k):
j = randbelow()
while j in selected:
j = randbelow()
selected_add(j)
result[i] = j
return result
print(sample(10**100, 10))
|
Go into sudo user, run couple of commands, go back to normal user in Python script
Question: The problem I've run into is that I want to temporarily get into the sudo
user, run a couple of commands, and then go back to a normal user and run the
commands in that mode.
You can find the script I'm gonna use it in here:
<https://github.com/Greduan/dotfiles/blob/master/scripts/symlinks.py>
Basically, when I'm installing the scripts under the `/bin` folder of my
dotfiles I need sudo access in order to make a symlink to that folder. You can
find this part of the script under the last for statement in the code.
However, since I do depend on some commands that use the current user as a
guideline to do stuff, I can't just run the entire script as `sudo`. Last time
I tried I got a lot of errors about a folder not existing.
Thanks for all the help you can provide.
Answer: If you don't mind installing an external dependency, the [`sh`
module](http://amoffat.github.io/sh/) makes this pretty simple:
import sh
sh.cp('foo.txt', 'bar.txt')
with sh.sudo:
sh.cp('foo2.txt', 'bar2.txt')
|
unable to run PyQt4 example
Question: I am trying to run a pyqt4 example through Notepad++. I asked this question
earlier ([Nothing happens when running PyQt4 example
code](http://stackoverflow.com/questions/16380923/nothing-happens-when-
running-pyqt4-example-code)), and ended up uninstalling Enthought Canopy and
all remnants of python and installing cygwin. Now, when I run the example code
I get the following error from npp's console. nppExec command -->
`C:\cygwin\bin\python2.7.exe -i "$(FULL_CURRENT_PATH)"`. The example code is
shown all the way at the bottom.
The closest I can get is to start cygwin x (type startx from the bash shell)
where I can get the example window to come up, although I am unable to exit
out of the window.
I feel like I am in over my head here, I just want to create some simple GUI's
and I am struggling just to get an example to work. Does Cygwin's python
installation lack the classic IDLE?
C:\cygwin\bin\python2.7.exe -i "C:\Users\Brian\Dropbox\Python\PYqt_practice.py"
Process started >>>
cygwin warning:
MS-DOS style path detected: C:\Users\Brian\Dropbox\Python\PYqt_practice.py
Preferred POSIX equivalent is: /cygdrive/c/Users/Brian/Dropbox/Python/PYqt_practice.py
CYGWIN environment variable option "nodosfilewarning" turns off this warning.
Consult the user's guide for more details about POSIX paths:
http://cygwin.com/cygwin-ug-net/using.html#using-pathnames
C:\Users\Brian\Dropbox\Python\PYqt_practice.py: cannot connect to X server
<<< Process finished. (Exit code 1)
================ READY ================
PyQt4 example code
import sys
from PyQt4 import QtGui
def main():
app = QtGui.QApplication(sys.argv)
w = QtGui.QWidget()
w.resize(250, 150)
w.move(300, 300)
w.setWindowTitle('Simple')
w.show()
sys.exit(app.exec_())
if __name__ == '__main__':
main()
Answer: PyQT4 and PyQT5 installed with Cygwin emulate directly what their equivalent
Linux packages do, meaning they **do** expect you to run an X server. Packages
dedicated to Windows obviously don't.
Basically you have two choices:
1. Give up on Cygwin and use packages dedicated to Windows, that don't need X server. (You could also run non-Cygwin python in Cygwin environment, but that's going to cause you some headaches, for example with Unicode.)
2. Install X server for Cygwin like this:
1. Get `xorg-server` package
2. Run `startx`
If this causes you problems, try:
2. Run `xwin -multiwindow` instead of `startx`
Now an icon should appear in your tray.
3. Click it with right mouse button
4. Hover to "applications"
5. Click `xterm`.
Congratulations! You just ran an `xterm` shell in X environment. See if your
application works now.
|
Python. Return current cursor position and position last left mouse click
Question: I want to be able to define the cursor position of the last left mouse click
as a point and the current cursor position as a point in real-world
coordinates. The code I have so far has the Tkinter import and Math import. I
have the GUI all sorted out for this part but I don't know how to define the
functions to be able to display it as a label for my GUI.
class PointFrame(Frame):
def __init__(self, master):
Frame.__init__(self, master)
self.LastClick= Label(self, text= "Last Point Clicked:")
self.LastClick.pack(side= LEFT)
self.CurrentPosition= Label(self, text="Cursor Point:")
self.CurrentPosition.pack(side= LEFT)
Need to create the functions below.
Answer: Something like this:
from tkinter import *
class App():
def __init__(self):
root = Tk()
self.last_point = (0, 0)
self.prev_var = StringVar(value='-:-')
self.curr_var = StringVar(value='-:-')
labels = Frame(root)
labels.pack()
Label(labels, text='Last Point Clicked: ').pack(side=LEFT)
prev = Label(labels, textvariable=self.prev_var)
prev.pack(side=LEFT)
Label(labels, text='Current point: ').pack(side=LEFT)
curr = Label(labels, textvariable=self.curr_var)
curr.pack(side=LEFT)
self.canvas = Canvas(root, background='white')
self.canvas.pack()
self.canvas.bind('<Button-1>', self.on_click)
self.canvas.bind('<Motion>', self.on_motion)
self.line = self.canvas.create_line(0, 0, 0, 0)
self.curr_text = self.canvas.create_text(0, 0)
root.mainloop()
def on_click(self, event):
# Last click in absolute coordinates
self.prev_var.set('%s:%s' % self.last_point)
# Current point in relative coordinates
self.curr_var.set('%s:%s' % (event.x - self.last_point[0], event.y - self.last_point[1]))
self.last_point = event.x, event.y
def on_motion(self, event):
self.canvas.coords(self.line, self.last_point[0], self.last_point[1], event.x, event.y)
self.canvas.coords(self.curr_text, event.x, event.y)
self.canvas.itemconfigure(self.curr_text, text="%s\n%s\n\n\n" % (event.x - self.last_point[0], event.y - self.last_point[1]))
App()
|
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