[Python-Dev] Re: closure semantics

[Zack Weinberg]

Skip Montanaro <skip at pobox.com> writes:

>     John> How about (to abuse a keyword that's gone unmolested for too long)
>
>     John>    global foo from def
>
>     John> to declare that foo refers a variable in a lexically enclosing
>     John> function definition?  This avoids to need to name a specific
>     John> function (which IMHO is just a source of confusion over the
>     John> semantics of strange cases) while still having some mnemonic value
>     John> (foo "comes from" an enclosing function definition).
>
> How do you indicate the particular scope to which foo will be bound (there
> can be many lexically enclosing function definitions)?  Using my example
> again:
>
>     def outer(a):
>         x = a
>         def inner(a):
>             x = 42
>             def innermost(r):
>                 global x from def       # <--- your notation
>                 x = r
>             print "  inner, x @ start:", x
>             innermost(random.random())
>             print "  inner, x @ end:", x
>         print "outer, x @ start:", x
>         inner(a)
>         print "outer, x @ end:", x
>
> how do you tell Python that x inside innermost is to be associated with the
> x in inner or the x in outer?

Maybe "global foo from <function_name>" ?  Or, "from function_name
global foo" is consistent with import, albeit somewhat weird.


I would never use this feature; I avoid nested functions entirely. 
However, as long as we're talking about this stuff, I wish I could
write "global foo" at module scope and have that mean "this variable
is to be treated as global in all functions in this module".

zw