python newbie

Bruno Desthuilliers bruno.42.desthuilliers at wtf.websiteburo.oops.com
Fri Nov 2 17:37:51 CET 2007


Bjoern Schliessmann a écrit :
> Jim Hendricks wrote:
(snip)
>> I see the global keyword that allows access to global vars in a
>> function, what I'm not clear on is does that global need to be
>> declared in the global scope,
> 
> You can't just declare in Python, you always define objects (and
> bind a name to them).

def toto():
   global p
   p = 42

Here I declared 'x' as global without defining it.

> Yes, globals need to be defined before you
> can access them using "global".

For which definition of 'defined' ?

 >>> p
Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
NameError: name 'p' is not defined
 >>> toto()
 >>> p
42
 >>>


>> 2) Everything is an object.  So then, why the distinction between
>> functions/variables and fields/methods.  
> 
> Because they are different things to achieve different goals. One
> holds data, the other does stuff.

Hem... I'm not sure you're really addressing the OP's question here. But 
anyway: in Python, everything's an object, so the only thing that makes 
functions a bit specials is that they are callable - as are classes, 
methods, and every instance of a class implementing __call__ FWIW. So 
saying 'variables holds data, functions do stuff' is unapplyiable to 
Python.

(snip)

>> If a module is an object, would not every function be a method of
>> that module and every variable be a field of that module?
> 
> They are.

functions are *not* methods of their module.



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