Python doctests: test for None

python doctest

The Python interpreter ignores None return values, so doctests do the same.

Test for is None instead:

>>> six_or_none(4) is NoneTrue

python doctest

Other option would be a direct check for None:

def six_or_none(val):    """    >>> six_or_none(6)    6    >>> six_or_none(4)    """    if val == 6:        return 6    return None

python doctest

Another alternative if you want something that looks like you might expect in your docs is:

>>> print(six_or_none(4))None

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