In Python how should I test if a variable is None, True or False

Question

I have a function that can return one of three things:

• success (True)
• failure (False)
• error reading/parsing stream

Answer 1

I would like to stress that, even if there are situations where if expr : isn't sufficient because one wants to make sure expr is True and not just different from 0/None/whatever, is is to be prefered from == for the same reason S.Lott mentionned for avoiding == None.

It is indeed slightly more efficient and, cherry on the cake, more human readable.

In [1]: %timeit (1 == 1) == True
38.1 ns ± 0.116 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)

In [2]: %timeit (1 == 1) is True
33.7 ns ± 0.141 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)