scopes? (is: I don't get it ...)

[Terry Reedy]

"Axel Bock" <news-and-lists at the-me.de> wrote in message
news:pan.2003.05.29.18.28.57.897132 at the-me.de...
> Am Thu, 29 May 2003 10:21:00 -0700 schrieb djw:
>
> > In order to assign to a global in a funtion, you must use the
global
> > statement, otherwise Python will assume you are assigning to a
local.
> > That's the way I understand it, anyway.
> >
> > test.py:
> > t1 = []
> > t2 = 0
> > def testme():
> >         global t2
> >         print t1
> >         print t2
> >         t2+=1

> whew, yes, thanks all of you! this helps ... ! :-)

Here are two more examples to consider...

>>> x=1
>>> def f():
...   x=2
...   global x
...
<stdin>:1: SyntaxWarning: name 'x' is assigned to before global
declaration
>>> f()
>>> x
2

# So put global statements at the top, even if not yet required.

>>> def g():
...   print x
...   x=3
...
>>> g()
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "<stdin>", line 2, in g
UnboundLocalError: local variable 'x' referenced before assignment

Some newbies expect printing of 2 instead of the error.  But the
interpreter reads the whole function text to classify variables as
local or not before starting again from the top to compile.

Terry J. Reedy