[Python-Dev] nonlocal keyword in 2.x? (original) (raw)

Fabio Zadrozny fabiofz at gmail.com
Thu Oct 22 17:32:37 CEST 2009

On Wed, Oct 21, 2009 at 10:56 PM, Mike Krell <mbk.lists at gmail.com> wrote:

Is there any possibility of backporting support for the nonlocal keyword into a  2.x release?  I see it's not in 2.6, but I don't know if that was an intentional design choice or due to a lack of demand / round tuits.  I'm also not sure if this would fall under the scope of the proposed moratorium on new language features (although my first impression was that it could be allowed since it already exists in python 3.

One of my motivations for asking is a recent blog post by Fernando Perez of IPython fame that describes an interesting decorator-based idiom inspired by Apple's Grand Central Dispatch which would allow many interesting possibilities for expressing parallelization and other manipulations of execution context for blocks of python code.  Unfortunately, using the technique to its fullest extent requires the nonlocal keyword. The blog post is here: https://cirl.berkeley.edu/fperez/py4science/decorators.html

Just as a note, the nonlocal there is not a requirement...

You can just create a mutable object there and change that object (so, you don't need to actually rebind the object in the outer scope).

E.g.: instead of creating a float in the context, create a list with a single float and change the float in the list (maybe the nonlocal would be nicer, but it's certainly still usable)

Cheers,

Fabio

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