Won't use global symbol table?

[Brian Quinlan]

> x = None
> def f():
>     # global x
>     if not x:
>         x = 1
>     return x
>
> Unless I uncomment that global line I get the error:
>
> File "ubtest.py", line 6, in f
>     if not x:
> UnboundLocalError: local variable 'x' referenced before assignment
>
> I thought python looked for a variable in the local symbol
> table, and if it couldn't find it there, went to the global
> (to the module) symbol table.  Why do I have to explicitly tell
> it to do so in this instance?

You can do anything that you want to a global without declaring it as such,
except for reassignment. A complete description of the global statement is
given at:

http://www.python.org/doc/current/ref/global.html

--
Brian Quinlan
Python and XSLT Developer
BrianQ at ActiveState.com

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