[Python-ideas] unpacking context managers in WITH statement

[Michael Foord]

On 3 February 2012 15:09, Yury Selivanov <yselivanov.ml at gmail.com> wrote:

> Hello,
>
> With the removal of "contextlib.nested" in python 3.2 nothing was
> introduced to replace it.  However, I found it pretty useful, despite the
> fact that it had its own quirks.  These quirks can (at least partially) be
> addressed by allowing unpacking syntax in the context manager.
>
> Consider the following snipped of code:
>
>  ctxs = ()
>  if args.profile:
>      ctxs += (ApplicationProfilerContext(),)
>  if args.logging:
>      ctxs += (ApplicationLoggingContext(),)
>  with *ctxs:
>      Application.run()
>


Well, I quite like this syntax and it does allow you to do something not
currently easily possible:

with *ctxs as tuple_of_results:
   ...

The use case is reasonably obscure however, and should this be possible:

with *ctx, other as tuple_of_results, another:
    ...

Michael



>
> As of now, without "nested" we have either option of reimplementing it, or
> to write lots of ugly code with nested 'try..except's.  So the feature was
> taken out, but nothing replaced it.
>
> What do you think guys?
>
> Thanks,
> Yury
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