[Python-3000] non-local assignment

[Chris Rebert]

It's been decided to go w/ the "nonlocal" keyword to declare outer
variables (ala the "global" keyword) rather than using an alternate
assignment operator (which was one of the competing proposals). It's
too late to make a change such as your suggestion because PEP 3104 (
http://www.python.org/dev/peps/pep-3104/ ), which proposed "nonlocal",
has already been accepted (and BDFL-blessed IIRC).

Furthermore, there's no precedent for Python operators to use both a
keyword and punctuation together like "set!", and "set" can't be used
instead as it's the name of a builtin type (in Py3K).

In the future, searching the list archives can be quite helpful.

- Chris Rebert


On Wed, May 28, 2008 at 10:55 PM, Daniel Wong <allyourcode at gmail.com> wrote:
> I'm confused by the section on "no alternate binding operator" in PEP
> 3099. On the one hand, it says no alternative binding operator will be
> considered; yet the link provided shows that Guido is in favor of
> developing a syntax for non-local assignment. Please excuse me if this
> post violates that rule. Here's my suggestion on what the syntax
> should look like:
>
> set! var val
>
> Scheme users will recognize this syntax, which has the distinct
> advantage of not being confusable with regular assignment; whereas,
> this is an unfortunate feature of :=, which Guido has already
> rejected.
>
> The way this is supposed to work is you go to the inner-most scope in
> which var is declared and change its value there to val. If var does
> not occur in any containing scope, you could raise an
> UndeclaredVariable exception.
>
> Thoughts?
>
> Daniel
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