Harishankar <v.harishan...@gmail.com> writes:
> When I run pychecker through my modules I get the message that
> comparisons with "False" is not necessary and that it might yield
> unexpected results.
Good advice.
> Yet in some situations I need to specifically check whether False was
> returned or None was returned. Why is comparison with False so bad?
Because it's almost always unnecessary and can yield unexpected results
:-)
In other words, the only purpose of the ‘bool’ type is to have values
explicitly designed for testing in Boolean conditions. Comparing them to
the literals is a code smell — indicating a poor design.
> # example code which matches both False and None
> if not var:
> # do something
Can you give a specific real-world example of why this is not good
enough? It's likely we can suggest better ways of achieving the broader
purpose.
> So how do you get around this? My functions return False and None
> under different circumstances.
Usually it is None that will be the special case, so it's usually better
to write something like::
result = foo()
if result is None:
# do special things
But that's just one possibility, and might not apply in your use case.
> Should I raise exceptions instead? I feel it's unnecessary clutter to
> use exceptions unless absolutely no other solution is available and
> yet I have doubts about the "False" value.
More details of the problem you're trying to solve would help with
giving specific advice.
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Ben Finney
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