compare classes and not class instances

[jantod]

I not only want to compare class *instances* but also the classes
themselves. Something like:

class T(object):
@classmethod
def __cmp__(cls, other):
return cmp(cls.__name__, other.__name__)
@instancemethod
def __cmp__(self, other):
return cmp(self.x, other.x)

class B(T): pass
class A(T): pass

sorted([B, A]) => [A, B]

My motivation for doing so is simply to sort classes based on their
names and not (as it seems is the default behaviour) on the order in
which they were created.

I guess I could always just do something like sorted(classes,
key=lambda cls: cls.__name__)...but where's the fun in that? :-)

[Peter Otten]

ja****@gmail.com wrote:

I not only want to compare class *instances* but also the classes
themselves. Something like: sorted([B, A]) => [A, B]

My motivation for doing so is simply to sort classes based on their
names and not (as it seems is the default behaviour) on the order in
which they were created.

I guess I could always just do something like sorted(classes,
key=lambda cls: cls.__name__)...but where's the fun in that? :-)

A class is just an instance of its metaclass. Therefore the metaclass is the
right place to implement the __cmp__() method:

class T: .... class __metaclass__(type):
.... def __cmp__(cls, other):
.... return cmp(cls.__name__, other.__name__)
.... class B(T): pass .... class A(T): pass .... class C(T): pass .... sorted([C, B, A])

[<class '__main__.A'>, <class '__main__.B'>, <class '__main__.C'>]

Peter

[jantod]

Awesome! Perfect!

Thanks
Janto