python code conventions

conventions.py

# put builtin libs first (and direct imports before 'from' imports)
import os
import sys
from threading import Thread

# then put 3rd party imports
import feedparser
from BeautifulSoup import BeautifulSoup

# and then project internal imports
import myapp.core
from myapp.libs import mymodule

# constants are all uppercase
VERSION = '1.1'
BUFFER_SIZE = 32


# class names are capitalized words
class MyClass(object):
    # method names are lowercase with underscores
    def do_something_useful(self):
        pass

    # except when using a framework with other conventions (twisted for example)
    def camelCaseFunction(self):
        pass


# function names follow the same conventions as methods
def my_leet_function():
    pass

# when testing for None, do it explicitely
if var is None:
    pass

# when testing for 0-length objects, do this way:
var = []
if not var:
    # var length is 0
    pass
var = ''
if not var:
    pass

# use isinstance to test an object's type
var = [1, 2, 3]
if isinstance(var, list):
    pass