Get class that defined method

import inspect

def get_class_that_defined_method(meth):
    for cls in inspect.getmro(meth.im_class):
        if meth.__name__ in cls.__dict__: 
            return cls
    return None

I don't know why no one has ever brought this up or why the top answer has 50 upvotes when it is slow as hell, but you can also do the following:

def get_class_that_defined_method(meth):
    return meth.im_class.__name__

For python 3 I believe this changed and you'll need to look into .__qualname__.