[Python-Dev] Re: closure semantics (original) (raw)

Skip Montanaro skip at pobox.com
Thu Oct 23 17:46:33 EDT 2003 

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?

Skip

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