Mix-In Class Methods At Run-Time

[bearophileHUGS at lycos.com]

I think it's possible, most of such kind of things are possible with
Python.
I'm not an expert yet in such kind of things, so this can be a starting
point for you (note the shadowing of m2, the class docstrings, etc).
Other people can give you something better or more correct.

class A:
    def m1(self): return "m1"
    def m2(self): return "m2"

class B:
    def m3(self): return "m3"

class P:
    def m2(self): return "m2b"
    def m4(self): return"m4"

def mixin(object, *classes):
    class NewClass(object.__class__):
        pass
    for C in classes:
        NewClass.__dict__.update(C.__dict__)
    object.__class__ = NewClass

foo = P()
print "Before:"
print "foo.__class__.__dict__.keys():", foo.__class__.__dict__.keys()
print "P.__dict__.keys():", P.__dict__.keys()
print "foo.m2():", foo.m2()
print "foo.m4():", foo.m4(), "\n"

mixin(foo, A, B)

print "After:"
print "foo.__class__.__dict__.keys():", foo.__class__.__dict__.keys()
print "P.__dict__.keys():", P.__dict__.keys()
print "foo.m1():", foo.m1()
print "foo.m2():", foo.m2()
print "foo.m3():", foo.m3()
print "foo.m4():", foo.m4()

Bye,
bearophile