[Python-ideas] Tweaking closures and lexical scoping to include the function being defined

[Jan Kaliszewski]

Terry Reedy dixit (2011-09-27, 21:17):

> defining a function
> inside a loop magically causes define-time binding of names in the
> body.

No, it does not cause such a binding. That is one of the cases the
proposition of this or that early-binding syntax comes back repeatedly:

    def strangish_factorission():
        chairs = []
        for spam in (1,2,3,4,5):
            def comfy_chair(fmt):
                # we naively try to make use of early binding here
                # but there is no such binding here
                result = fmt % spam
                return result
            chairs.append(comfy_chair)
        return chairs

    for comfy_chair in strangish_factorission():
        print comfy_chair('%d'),

-- will print "5 5 5 5 5", not "1 2 3 4 5".

To obtain the latter you need to use eigher default argument hack (which
is ugly and unsafe in some situations) or a closure (which for now needs
another nested scope, which is even worse in terms of readability).

Cheers,
*j