In conditionals change from implicit check for False (or None) to explicit check "is None".

References:
PEP-8 programming recommendations
"Comparisons to singletons like None should always be done with is or is not, never the equality operators...
Also, beware of writing if x when you really mean if x is not None"
http://www.python.org/dev/peps/pep-0008/

http://stackoverflow.com/questions/7816363/if-a-vs-if-a-is-not-none