Python subclass determined at runtime

meta.py

# Based on http://python-3-patterns-idioms-test.readthedocs.io/en/latest/Metaprogramming.html

class P1(object):
    name = 'Parent1'


class P2(object):
    name = 'Parent2'


K = 'P1'


class MetaBase(type):
    def __new__(mcl, name, bases, nmspc):
        return super(MetaBase, mcl).__new__(mcl, name, bases, nmspc)


class Meta(MetaBase):
    def __new__(mcl, name, bases, nmspc):
        bases = (P1,) if K is 'P1' else (P2,)
        return super(Meta, mcl).__new__(mcl, name, bases, nmspc)


class C(object):
    __metaclass__ = Meta

c = C()
print(c.__class__.__bases__, c.__class__)  # ((<class '__main__.P1'>,), <class '__main__.C'>)
print(c.name)  # Parent1