Classes and modules are singletons?

[castironpi at gmail.com]

On Mar 5, 8:31 pm, Steven D'Aprano <st... at REMOVE-THIS-
cybersource.com.au> wrote:
> On Wed, 05 Mar 2008 21:05:31 -0500, Terry Reedy wrote:
> > If I understand your question, classes are not singletons:
> >>>> ll=[]
> >>>> for i in range(2):
> >  import string
> >  ll[i]=string
>
> Where's the IndexError? :-)
>
> >>>> ll[0] is ll[1]
> > True
>
> But yes, modules are singletons in that way, at least if you go through
> the import mechanism.
>
> >>>> for i in range(2):
> >  class C: pass
> >  ll[i] = C
>
> >>>> ll[0] is ll[1]
> > False
>
> Ah, but each time around the loop you create a *new class* that just
> happens to be called C. An alternative way to see similar behaviour is:
>
> def foo(x=None):
>     class C(object):
>         X = x
>     return C
>
> Naturally foo() is foo() gives False -- although both classes are called
> C, they are different classes that just happen to have the same state.
>
> I accept my question about classes being singletons is not well-formed,
> not even in my own mind. I guess one way of asking is, for any two class
> objects (not instances) C1 and C2, does "C1 == C2" imply "C1 is C2"?

>>> class metaC( type ):
...     def __eq__( self, other ):
...             return random.choice([ True, False ])
...
>>> class C( metaclass= metaC ):
...     pass
...
>>> import random
>>> C==C
True
>>> C==C
False
>>> C==C
False
>>> C==C
True
>>> C==C
False
>>>

You made me think of this.  What relevance it has is open to
debate.  ...In a separate thread.

http://en.wikipedia.org/wiki/Relevance

It's my Signal-channel signal signal.