[Tutor] Bitten by lexical closures

[Chad Crabtree]

Are you just trying to make a continuation?

On 5/3/06, Igor <igor at c-base.org> wrote:
> Hi.
>
> And I thought I understood python pretty well. Until I got hit by this:
>
> >>> def f(x):
> ...   print x
>
> >>> cb = [lambda :f(what) for what in "1234"]
> >>> for c in cb:c()
> 4
> 4
> 4
> 4
>
> And even this works
>
> >>> what = "foo"
> >>> for c in cb:c()
> foo
> foo
> foo
> foo
>
> I expected the output to be 1 2 3 4. Now I understand the cookbook
> recipe for currying:
> def curry(func, *args, **kwds):
>     def callit(*moreargs, **morekwds):
>         kw = kwds.copy()
>         kw.update(morekwds)
>         return func(*(args+moreargs), **kw)
>     return callit
>
> cb = [curry(f,what) for what in "1234"]
>
> gives the right functions.
>
> Regards,
> Igor
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