On Sun, 29 May 2011 11:47:26 +0200, Wolfgang Rohdewald wrote:
> On Sonntag 29 Mai 2011, Henry Olders wrote:
>> It seems that in Python, a variable inside a function is global unless
>> it's assigned.
>
> no, they are local
I'm afraid you are incorrect. Names inside a function are global unless
assigned to somewhere.
>>> a = 1
>>> def f():
... print a # Not local, global.
...
>>> f()
1
By default, names inside a function must be treated as global, otherwise
you couldn't easily refer to global functions:
def f(x):
print len(x)
because len would be a local name, which doesn't exist. In Python, built-
in names are "variables" just like any other.
Python's scoping rule is something like this:
If a name is assigned to anywhere in the function, treat it as a local,
and look it up in the local namespace. If not found, raise
UnboundLocalError.
If a name is never assigned to, or if it is declared global, then look it
up in the global namespace. If not found, look for it in the built-ins.
If still not found, raise NameError.
Nested scopes (functions inside functions) make the scoping rules a
little more complex.
If a name is a function parameter, that is equivalent to being assigned
to inside the function.
--
Steven
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