difference between != and is not

[deanhystad]

None is a singleton. There is only one None object. is/is not None checks if an object is the None object or not. Checking ihe value, which is what != does, is superfluous. No object other than None wiill == None.

In addition to None, True and False are singltons and you should never test ==True or == False, but rather is True or is False. Well, you should not do that either unless you really want to know if something is the True object or the False object.