[Python-Dev] multi-with statement

[Fredrik Johansson]

On Sat, May 2, 2009 at 9:01 PM, Georg Brandl <g.brandl at gmx.net> wrote:
> Hi,
>
> this is just a short notice that Mattias Brändström and I have finished a
> patch to implement the previously discussed and mostly warmly welcomed
> extension to with's syntax, allowing
>
>   with A() as a, B() as b:
>
> to be written instead of
>
>   with A() as a:
>       with B() as b:
>
> This syntax was chosen (over "with A(), B() as a, b:") because it has more
> syntactical similarity to the written-out version.  Also, our current uses
> of "as" all have only one expression on the right.
>
> The patch implements it as a simple AST transformation, which guarantees
> semantic equivalence.  It is at <http://codereview.appspot.com/53094>.
>
> If there is no strong opposition, I will commit it and port it to py3k
> before 3.1 enters beta stage.
>
> cheers,
> Georg

I was hoping for the other syntax in order to be able to create a
nested context in advance as a simple tuple:

with A, B:
    pass

context = A, B
with context:
    pass

(I.e. a tuple, or perhaps any iterable, would be a valid context manager.)

With the syntax in the patch, I will still have to implement a custom
nesting context manager to do this, which sort of defeats the purpose.

Fredrik