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Date: Wed, 16 Nov 2011 08:34:02 +1100
Subject: Re: suppressing import errors
From: Chris Angelico <rosuav@gmail.com>
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:15742

On Wed, Nov 16, 2011 at 8:20 AM, David Riley <fraveydank@gmail.com> wrote:
>   =A0 =A0Comparisons to singletons like None should always be done with
> =A0 =A0 =A0'is' or 'is not', never the equality operators.
>
> =A0 =A0 =A0Also, beware of writing "if x" when you really mean "if x is n=
ot None"
> =A0 =A0 =A0-- e.g. when testing whether a variable or argument that defau=
lts to
> =A0 =A0 =A0None was set to some other value. =A0The other value might hav=
e a type
> =A0 =A0 =A0(such as a container) that could be false in a boolean context=
!

It's probably quicker to execute "if x is None" than "if x"
(presumably the former just compares the two pointers). On the other
hand, it's more compact to leave off the "is None". And on the
gripping hand, neither "quicker to execute" nor "more compact" equates
to "more Pythonic".

ChrisA