suppressing import errors

[Chris Angelico]

On Wed, Nov 16, 2011 at 8:20 AM, David Riley <fraveydank at 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".

ChrisA