Class Help

[Peter]

Ivan Shevanski wrote:

>To continue with my previous problems, now I'm trying out classes.  But I 
>have a problem (which I bet is easily solveable) that I really don't get.  
>The numerous tutorials I've looked at just confsed me.For intance:
>
>  
>
>>>>class Xyz:
>>>>        
>>>>
>...     def y(self):
>...             q = 2
>...
>  
>
>>>>Xyz.y()
>>>>        
>>>>
>Traceback (most recent call last):
>  File "<stdin>", line 1, in ?
>TypeError: unbound method y() must be called with Xyz instance as first 
>argument
>(got nothing instead)
>
>
>So. . .What do I have to do? I know this is an extremley noob question but I 
>think maybe if a person explained it to me I would finally get it =/
>
>  
>
You have to create an instance of the class before it can be called. Ex:
class foo:
    def bar(self):
        print "Hello, World!"
    foo().bar()

This is because foo is a reference to a classobj, however, when you call 
the class, it becomes an instance.

Ex:
 >>> type(foo)
<type 'classobj'>
 >>> type(foo())
<type 'instance'>

When an instance is created it tells Python to pass the instance as the 
first argument (self).
Otherwise it gives it None or something similer. (Note that im not 100% 
sure about why it does'nt work, im just guessing from the way it _seems_ 
to work. I have read no documentation on this.

If you want it to work before you create an instance, then you can do 
that with
class foo:
    @classmethod
    def bar(self):
       print "Hello, World!"

or the older (but exactly the same):
class foo:
    def bar(self):
       print "Hello, World!"
    bar = classmethod(bar)

>thanks in advance,
>
>-Ivan
>
>  
>
HTH,
Peter