Re: suppressing import errors

References	(4 earlier) <4EC2B656.7050902@sequans.com> <0601B8C7-9AEF-443A-A149-0F7D356345EF@gmail.com> <CAPTjJmrP7fMg9UfxdsR=5j6EW4yFKf8gR4xYQD5zDwMUVxdmjw@mail.gmail.com> <F8266E63-F932-4216-9E33-8333C1D62E43@gmail.com> <CAPTjJmofCYDy5rLPzCJPNMj5qM_KAc9606RmLKAtcaySjwf92w@mail.gmail.com>
Date	2011-11-15 21:42 +0000
Subject	Re: suppressing import errors
From	Arnaud Delobelle <arnodel@gmail.com>
Newsgroups	comp.lang.python
Message-ID	<mailman.2752.1321393344.27778.python-list@python.org> (permalink)

Show all headers | View raw

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

Back to comp.lang.python | Previous | Next | Find similar | Unroll thread

Thread

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

csiph-web