Closures in python
joshway_without_spam at myway.com
Thu Sep 18 15:19:58 CEST 2003
Hallvard B Furuseth <h.b.furuseth(nospam)@usit.uio(nospam).no> wrote:
> 'closure' is a much-abused word.
> This is a closure over foo's x variable:
> def foo():
> x = 3
> def bar():
> x += 1
> return x
> return bar
> f = foo()
> print f() # print 4
> g = foo()
> print f() # print 5
> print g() # print 4
> ...or it would be, if it worked.
Python does have closures; the trouble is you can't rebind variables
defined in arbitrary scopes--you can only rebind locals and globals.
So you need some indirection for it to work:
>>> def foo():
... x = 
... def bar():
... x += 1
... return x
... return bar
>>> f = foo()
>>> g = foo()
This is actually one of my biggest complaints about Python. I'd like
syntactic disambiguation between definition and assignment in order to
have control over which scope you're assigning into.
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