Update app.py

app.py

@@ -271,7 +271,7 @@ def mychain_mine_block_send(balance, chain_r=None,chain_n=None):
                 'previous_hash': block['previous_hash']
                }
 
-    previous_post = mychain_sned.print_previous_block()
+    previous_post = mychain_send.print_previous_block()
     
     block = {'index': previous_post['index'],
             'timestamp': previous_post['timestamp'],