What is a classmethod for?

[Ian Bicking]

On Sun, 2002-06-02 at 19:06, Dennis Peterson wrote:
> > The point is that you can call class methods *without* creating an
> > instance:
> 
> >C.foo()
> 
> But you can do that with a static method:
> 
> class C:
>     def foo(x):
>         print x
>     foo = staticmethod(foo)
> 
> C.foo(1)

Maybe a better example would be per-class caching.  Like:

class C:
    cache = {} # Contains values of (expire_time, cache_value)
    def cleanCache(klass):
        for key, (expire_time, value) in klass.cache.items():
            if expire_time < time.time(): del[klass.cache[key]]

In general it only makes sense when you use class variables -- just like
if you don't use any instance variables it might make more sense to use
a plain function instead of a method.

  Ian