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Date: Tue, 15 Nov 2011 21:42:22 +0000
Subject: Re: suppressing import errors
From: Arnaud Delobelle <arnodel@gmail.com>
To: Chris Angelico <rosuav@gmail.com>
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:15743

On 15 November 2011 21:34, Chris Angelico <rosuav@gmail.com> wrote:
> On Wed, Nov 16, 2011 at 8:20 AM, David Riley <fraveydank@gmail.com> wrote=
:
>> =C2=A0 =C2=A0 =C2=A0Comparisons to singletons like None should always be=
 done with
>> =C2=A0 =C2=A0 =C2=A0'is' or 'is not', never the equality operators.
>>
>> =C2=A0 =C2=A0 =C2=A0Also, beware of writing "if x" when you really mean =
"if x is not None"
>> =C2=A0 =C2=A0 =C2=A0-- e.g. when testing whether a variable or argument =
that defaults to
>> =C2=A0 =C2=A0 =C2=A0None was set to some other value. =C2=A0The other va=
lue might have a type
>> =C2=A0 =C2=A0 =C2=A0(such as a container) that could be false in a boole=
an 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".

It's idiomatic to write "x is None" when you want to know whether x is None=
.

--=20
Arnaud