String representation of a class in Python 3

Question

I'd like my classes to have a string representation which is based on a class variable (which may be different in derived classes). This answer suggests that metaclasses might be the way to go:

class MC(type):
    def __repr__(self):
        return 'Wahaha!'

class C():
    __metaclass__ = MC

print(C)

But this doesn't work in Python 3, returning

<class '__main__.C'>

instead of Wahaha!. Can someone explain to me what changed between Python 2 and 3 and how to go about it in Python 3?

Side note: PEP 8 recommends using 4 spaces per indentation, not 2. As a general rule, doing the same thing as virtually everybody else makes life simpler. I did edit your question, so as to not make newcomers believe that it is a good idea to stray away from the standard recommendation. — Eric O Lebigot, Jun 02 '15 at 00:13

score 5 · Accepted Answer · edited Jun 02 '15 at 00:14

5

What changed is how the metaclass is declared in 3.x.

class C(metaclass=MC):
    pass

edited Jun 02 '15 at 00:14

Eric O Lebigot

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answered Jun 02 '15 at 00:07

Ignacio Vazquez-Abrams

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String representation of a class in Python 3

1 Answers1