Why this throws an UnboundLocalError ?

[Marc Aymerich]

Dear all,

I have a very simple module

glic3 at e4200:# cat globalstate.py
GLOBAL = 0

def update():
    GLOBAL += 1


however it doesn't work!!

glic3 at e4200:# python
Python 2.7.3 (default, Aug  1 2012, 05:14:39)
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import globalstate
>>> globalstate.update()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "globalstate.py", line 4, in update
    GLOBAL += 1
UnboundLocalError: local variable 'GLOBAL' referenced before assignment


And I don't know why :(
Anyone ?

Thanks!!
-- 
Marc