What's wrong with `is not None`?

[Stefan Behnel]

Frans Englich schrieb:
> What is the equivalent expression which is more secure; `!= None`?

Note that this is not necessarily equivalent. '!=' and '==' possibly run
method calls on objects which can be costly depending on their
implementation and can even raise exceptions if called with None. If I
want to check for None, I always do it with "is". It's a constant after all...

Stefan