checking if two things do not equal None

Steven D'Aprano steve+comp.lang.python at
Sun Mar 30 04:04:14 CEST 2014

On Sat, 29 Mar 2014 17:07:20 -0400, Roy Smith wrote:

> I certainly agree that things like
>> if a is not b is not None: ...
> belong in an obfuscated coding contest. 

Apart from the fact that I got it wrong (that's what happens when I post 
at 6am after being up all night, thanks for the correction Lele), if you 
consider chained comparisons to be "obfuscated", I think you're not 
really fluent at Python. The OP even suggested  `a != None != b` so I 
think that (s)he at least understands chained comparisons.

However, I agree with Johannes that inverted conditions (using "not") are 
sometimes harder to reason about than "regular" conditions.

Steven D'Aprano

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