Changing the repr() of a class?

[Alex Martelli]

Donald McCarthy wrote:

> I would like to alter the way python displays what a class is. I can do
> this for an instance of a class using __repr__ but I don't know how to do
> this for a class.

You do it by defining a custom metaclass.  Python 2.2 of course:

class FunkyReprMeta(type):
    def __repr__(cls):
        return "My wonderful class %s" % cls.__name__

class FunkyReprObject:
    __metaclass__ = FunkyReprMeta


class C(FunkyReprObject):
    "whatever you want here"


print C


this emits "My wonderful class C" and has otherwise just the semantics
of newstyle classes.  A class is an instance of its metaclass, after all, so
that's how you define how/what happens when a class object gets
printed, added to something, etc -- define special methods in its
metaclass.  Instead of deriving from FunkyReprObject, by the way,
you may prefer to define __metaclass__ in the class-body of C directly,
or as a module-level global variable.


Alex