Dave Angel <da...@ieee.org> dixit:
> Maybe a more complex example might show the various linkages.
>
> glob = 42
>
> def outer(parm1):
> free = 12
> free3 = 19
> def inner(parm2, parm3=free3):
> print "global", glob, ", free vars", parm1, free, free3, ",
> locals", parm2, parm3
> free = 49
> free3 = 48
> return inner
>
> newfunc = outer(10)
> newfunc(45)
>
>
> produces output:
> global 42 , free vars 10 49 48 , locals 45 19
>
> So when the inner() function is actually called, glob is just a global.
> parm1, fre, and free3 hold the values they ended up with when outer()
> returned, and local parm2 is passed by top-level code, while local parm3
> gets its default value assigned when "def inner(...) was executed.
>
> Notice that the free variables free, free3, and parm1 are referring to
> the function's ending state, not to the state when the function was
> defined. This has an impact when you've got inner being defined in a
> loop. And this example could be made more complex if outer() is a
> generator, in which case it may not have actually ended when inner gets
> called.
>
> HTH
> DaveA
Great example, thank you.
By the way, do you know the idiom:
def makeInc(start):
def inc():
inc.n += 1
print inc.n
inc.n = start
# 'start' may change now
# ...
return inc
inc= makeInc(start=3)
inc()
I find it much nicer than a pseudo default value, for it explicitely shows that
'n' is, conceptually speaking, an attribute of the func (read: a closure
upvalue). Let's take advantage of the fact python funcs are real objects!
Denis
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