[BangPypers] Enclosing lexical context

Anand Chitipothu anandology at gmail.com
Thu Apr 15 20:03:04 CEST 2010

2010/4/15 Picachu Nioto <picachu.nioto at gmail.com>:
> Could some one explain to me this sentence, I read in an example online
> "Python doesn't implement assignment of variables bound in an enclosing
> lexical context"
> Example,
> a=[b]

Consider the following example:

a = 1
def f():
   b = 2
    def g():
        c = 3

        # this function can access all a, b and c variables.
        print a, b, c

        # c can be reassigned
        c = 42

        # a can be reassigned only if it is declared as global,
otherwise it is considered as local to this function
        global a
        a = 42

       # b can't be reassigned because it is neither local nor global.
It is in the enclosing lexical context

SInce b can't be reassigned, the work-around is to modify the object
instead of reassigning.

However, python3.0 added a new "nonlocal" construct to enable that.
With python 3, you should be able to say:

nonlocal b
b = 42


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