partial-bound-method

bound-unbound-partial

import sys
from functools import partial


class A(object):
    def meth(self):
        return 'orig'


def newmeth(self):
    assert isinstance(self, A)
    return 'new'


a = A()
assert a.meth() == 'orig'
a.meth = partial(newmeth, a)
assert a.meth() == 'new'
a.meth = partial(A.meth, a)
assert a.meth() == 'orig'

print >>sys.stderr, 'OK'