nested functions - access to variables?

[Oleg Leschov]

hi,

suppose we have a program like this one:
-cut-
g = 100

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

a()
print g
-cut-

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

If curious, the original function parses certain syntax constructing
list-based
tree from it. I do not want to pollute real global namespace with
function-specific subprograms and variables..

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

The other question - will there be (or already is) in Python something
similar in functionality to variant types from FPLs?
not counting different perversions with checking for None...