[Python-Dev] Explicit Lexical Scoping (pre-PEP?)

[Talin]

Talin wrote:
> Some alternatives:
> 
>      use x
>      using x
>      with x     -- recycle a keyword?
>      reuse x
>      use extant x
>      share x
>      common x
>      same x
>      borrow x
>      existing x
> 
> Although, to be perfectly honest, the longer this discussion goes on, 
> the more that I find that I'm not buying Guido's argument about it being 
> better to define this at the point of use rather than at the point of 
> definition. I agree with him that "point of use" is more Pythonic, but 
> I'm also beginning to believe that there are some good reasons why many 
> other languages do it the other way.
> 
> Part of the reason why its so hard to name this feature is that it's 
> real name is something like "Hey, Python, you know that cool funky thing 
> you do with defining variables in the same scope as they are assigned? 
> Well, don't do that here."

(Followup to my own comment)

There are really 3 places where you can indicate that a variable is to 
be reused instead of redefined: 1) The point of definition in the outer 
scope, 2) A declaration in the inner scope, and 3) The actual point of 
assignment.

#1 is what I've been pushing for, #2 is what most of the discussion has 
been about, #3 has been talked about a little bit in the context of an 
augmented assignment operator.

I actually like #3 a little better than #2, but not with a new operator. 
I'm thinking more along the lines of a keyword that modifies and 
assignment statement:

    rebind x = 10

Other possible keywords are: modify, mutate, change, update, change, etc...

My gut feeling is that most code that wants to use this feature only 
wants to use it in a few places. A good example is fcgi.py (implements 
WSGI for FastCGI), where they use a mutable array to store a flag 
indicating whether or not the headers have already been sent.

-- Talin