Python Lines and indentation

How to create a block in python?

• No braces to indicate blocks of code for class and function or flow control.
• Blocks of code are represented by line indentation.
• Number of spaces in indentation is different (or variable), but all statements in the block must be indented the same number of spaces.

Valid block:

if True:
   print "true"
else:
 print "false"

Python program for valid block:

#!/usr/bin/python                                                               
                                                                                
import random                                                                   
import time                                                                     
import threading                                                                
                                                                                
def display_message(count):                                                     
    random_sec = random.randint(1,4)                                            
    print "thread %d is going to sleep for %d seconds" % (count, random_sec)    
    time.sleep(random_sec)                                                      
    print "thread %d is resuming back" % count                                  
                                                                                
for count in range(5):                                                          
    thr = threading.Thread(target=display_message, args=(count,))               
    thr.start()                                                                 

$ python thread_test1.py 
thread 0 is going to sleep for 2 seconds
thread 1 is going to sleep for 3 seconds
thread 2 is going to sleep for 3 seconds
thread 3 is going to sleep for 2 seconds
thread 4 is going to sleep for 1 seconds

thread 4 is resuming back
thread 0 is resuming back
thread 3 is resuming back
thread 1 is resuming back
 thread 2 is resuming back

Invalid block

if True:
    print "line1"
    print "line2"
else:
    print "line3"
  print "line4"

Python program for invalid block:

#!/usr/bin/python                                                               
                                                                                
import random                                                                   
import time                                                                     
import threading                                                                
                                                                                
def display_message(count):     
    #indentation is not same in all lines of this method.                                                
    random_sec = random.randint(1,4)                                            
      print "thread %d is going to sleep for %d seconds" % (count, random_sec)  
     time.sleep(random_sec)                                                     
     print "thread %d is resuming back" % count                                 
                                                                                
for count in range(5):                                                          
    thr = threading.Thread(target=display_message, args=(count,))               
    thr.start()                                                                 

$ python thread_test1.py 
  File "thread_test1.py", line 9
    print "thread %d is going to sleep for %d seconds" % (count, random_sec)
    ^
IndentationError: unexpected indent

Python Coding Style

• PEP 8 is the python style guide and promotes a better readable coding style. most projects are adhere to PEP8.
• Wherever indentation is required, use 4-space indentation
• Don't use tabs
• Each line don't exceed 79 charaters, wrap lines less than 79 chars.
• Use documentation strings (docstrings).
• blank lines need to be used to differentiate functions and classes, and blocks of code inside functions.
• Wherever complex logic, place the comments to understand the code logic.
• Space should be included before and after operators but not inside brackets (a+b), and after commas.
• Naming classes and functions in consistent, CamelCase for classes and lower_case_with_underscores for functions and methods.
• ASCII encoding works best, don't use fancy encoding

How to ensure that python code is followed above coding styles?

$ . venv/bin/activate
[venv]$cd project-folder
[venv]$tox -e pep8

pep8 develop-inst-nodeps: folder@4e65b339c7cf303269ceef34b1e550c0eafa9dae#egg=project-folder,typing==3.6.2,unicodecsv==0.14.1,unittest2==1.1.0,urllib3==1.22,warlock==1.2.0,websocket-client==0.44.0,wrapt==1.10.11
pep8 runtests: PYTHONHASHSEED='2009495220'
pep8 runtests: commands[0] | flake8
pep8 runtests: commands[1] | bash -c tools/check_duplicate_jinja_blocks.sh
_____________________________________________________________________________________________________ summary _____________________________________________________________________________________________________
  pep8: commands succeeded
  congratulations :)