Python `if x is not None` or `if not x is None`?

Posted by orokusaki on Stack Overflow See other posts from Stack Overflow or by orokusaki
Published on 2010-04-26T03:10:30Z Indexed on 2010/04/26 3:13 UTC
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boolean-expression

I've always thought of the if not x is None version to be more clear, but Google's style guide implies (based on this excerpt) that they use if x is not None. Is there any minor performance difference (I'm assuming not), and is there any case where one really doesn't fit (making the other a clear winner for my convention)?*

*I'm referring to any singleton, rather than just None.

...to compare singletons like None. Use is or is not.

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