UnboundLocalError

Camellia breakfastea at gmail.com
Sat Nov 11 09:03:07 CET 2006


Oh how can I thank you enough, you make my day:)
According to what you said I finally figure it out, it is the same as:

<code>
b = 1
def a():
    b = b #no good:)
</code>

So in every day programming I should avoid using the same name for
different types of objects because they will step on each other, right?

On Nov 11, 6:18 pm, Gabriel Genellina <gagsl... at yahoo.com.ar> wrote:

On Nov 11, 6:18 pm, Gabriel Genellina <gagsl... at yahoo.com.ar> wrote:
> At Saturday 11/11/2006 02:35, Camellia wrote:
>
> >But sorry I'm so dumb I can't say I really understand,
> >what do I actually do when I define a function with its name "number"?Don't apologize, Python is a lot more dumb than you. It obeys very
> simple rules (a good thing, so we can clearly understand them, once
> we know them).
> Recalling your previous example:
>
> > > >> def main():
> > > >>    number = number()Python first scans the source code looking for assigned-to names.
> That is, names to the left of equal signs. Those names, plus the
> function formal parameters, make the list of "local names". Any other
> names referenced are assumed to be globals, that is, living outside
> your function. (That's not entirely true but enough for now).
> Notice that "number" is a local name because it's assigned to; it
> doesn't matter whether a global name "number" exists or not.
> When the code is executed, the "number" to the right references the
> local name, which has not been assigned to yet - that's why you get
> an UnboundLocalError. "number" can't be a global name when used on
> the right hand side, and a local name when used on the left hand
> side. It's simple: it is local, or not, but not both.
>
> >why does a name of a function has something to do with a variable?Notice also that it does not matter *what* kind of object a name
> refers to: it may be a function, a class, an object instance,
> whatever. Inside a function, by example, a local name "a" may be
> bound at most to a single object at a time, it doesn't matter its
> type. A local name "a" can't refer to an integer and a class at the same time.
> The left hand side of an assign statement *always* uses local names,
> except when you declare a name to be global by using the "global" keyword.
> And notice also that I've never used the word variable.
>
> >Oh wait can I do this in Python?:
> ><code>
> >def a():
> >     def b()
> ></code>
>
> >so the b() will appear to be a local function which is the possible
> >cause of my little own error because the compiler will interpret the
> >number() as a local function but a global one?Yes, you can. Python has "lexically nested scopes". The simple
> local/global rule of above is a bit more complicated: when a name is
> not local, it is searched inside the enclosing functions, then in the
> containing module's global namespace, and last in the builtin names.
> And yes, b is local to a, so it effectively hides any external b that
> could be in outer scopes.
>
> --
> Gabriel Genellina
> Softlab SRL
>
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