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Re: suppressing import errors

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  Re: suppressing import errors Arnaud Delobelle <arnodel@gmail.com> - 2011-11-15 21:42 +0000

#15743 — Re: suppressing import errors

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:
>>      Comparisons to singletons like None should always be done with
>>      'is' or 'is not', never the equality operators.
>>
>>      Also, beware of writing "if x" when you really mean "if x is not None"
>>      -- e.g. when testing whether a variable or argument that defaults to
>>      None was set to some other value.  The other value might have a type
>>      (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".

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

-- 
Arnaud

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