[Python-ideas] "maybe import"?

[Gregory P. Smith]

On Thu, Dec 26, 2013 at 5:57 PM, Amber Yust <amber.yust at gmail.com> wrote:

> It's a fairly standard pattern to see things like this:
>
>     try:
>         import foo
>     except ImportError:
>         foo = None
>
> (and of course, variants with from...import et cetera). These can
> potentially add a lot of clutter to the imports section of a file, given
> that it requires 4 lines to do a conditional import.
>
> It seems like it'd be useful and clean to have a syntax that looked like
> this:
>
>     maybe import foo
>     from bar maybe import baz
>     from qux maybe import quy as quz
>
> Where the behavior would essentially be as above - attempt to run the
> import normally, and in cases where the import fails, map the name to a
> value of None instead. Users who want a different behavior are still free
> to use the long-form syntax. A possibly variant might be to also only run
> the import if the name isn't already bound, so that you could do something
> like...
>
>     from frobber_a maybe import frob as frobber
>     from frobbler_b maybe import frobble as frobber
>     from frobber_c maybe import frobit as frobber
>
> ...to potentially try different fallback options if the first choice for
> an interface provider isn't available.
>
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Such idioms are common.  Though I don't think we should encourage their use.

That said, if you want to have something like this added it should not use
a new keyword ("maybe") but should use what we have. These look odd to me
but are possible ideas:

import foo else foo = None
from foo import bar else bar = None

that reuse of else on import statements would also enable the other idiom
of importing one of several things to a single name:

import foo as x else import bar as x

Just tossing those out there. I'm not convinced this is worth adding to the
language.

-gps
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