nested functions - access to variables?

[Andrew Koenig]

Oleg> suppose we have a program like this one:

Oleg> g = 100

Oleg> def a():
Oleg>     g = 200
Oleg>     def b():
Oleg>         global g
Oleg>         g = 300
Oleg>     b()
Oleg>     print g

Oleg> a()
Oleg> print g


Oleg> this thing prints 200 300, while i really need it to print 300 100.
Oleg> When I remove 'global g', it prints 200 100, as one should expect.

...

Oleg> So the question is, how to access function's variables from its
Oleg> nested function?  Python version is 2.2.

A function cannot affect the name binding in its surrounding context,
unless that context is global.  So there is no way for b() to change
the binding of the variable g defined in a().

However, a function *can* change the value of the object to which
a name in the surrounding context is bound, as long as it remains
the same object.  Which means that you can do this:

        g = 100
        def a():
            g = [200]
            def b():
                g[:] = [300]
            b()
            print g

        a()
        print g

and it will print [300] followed by 100.

-- 
Andrew Koenig, ark at research.att.com, http://www.research.att.com/info/ark