There's an analysis of the topic at developerworks:
http://www-106.ibm.com/developerworks/linux/library/l-pycon?t=grl,l=252,p=iterators
On (10/04/02 08:41), Bob Miller wrote:
> Those of you who were at the clinic last night know that I
> was asking for help on a weird limitation of Python.
>
> The problem: Consider the function, foo(), in this C program.
>
> #include <stdio.h>
>
> int foo()
> {
> static int n = 0;
> return ++n;
> }
>
> main()
> {
> int n1 = foo();
> int n2 = foo();
> printf("%d %d\n", n1, n2);
> return 0;
> }
>
> It keeps state around between calls, but does not have extra names in
> any nonlocal namespaces.
>
> How would you write a function in Python that does the same?
> (Note, I don't want a solution that only returns successive numbers.
> I might use this to return successive lines of a file or calculate
> successive permutations of a sequence or whatever.)
>
> The solution: For some reason, this apparently simple problem doesn't
> have any good solutions (that I'm aware of). Here's the best I can
> do.
>
> def foo():
> n = [0]
> def bar():
> n[0] += 1
> return n[0]
> return bar
> foo = foo()
>
> That reuses the single global name, foo. First, foo holds a function
> that returns the function we need. Then we set foo to the returned
> function. The original function is not accessible, AFAIK.
>
> --
> Bob Miller K<bob>
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