bar.py

import foo


class Bar(object):

	def __init__(self):
		print "in bar.Bar.init"

	def run(self, msg):
		print "in bar.Bar.exec", msg


def bar(msg):
	print "in bar.bar", msg


foo.Foo = Bar
foo.foo = bar

baz.py

import foo


class Baz(foo.Foo):

	def __init__(self):
		print "in baz.Baz.init"

	def run(self, msg):
		print "in baz.Baz.exec", msg


def baz(msg):
	print "in baz.baz", msg

foo.py

class Foo(object):

	def __init__(self):
		print "in foo.Foo.init"

	def run(self, msg):
		print "in foo.Foo.exec", msg


def foo(msg):
	print "in foo.foo", msg

main.py

def test():
	i = foo.Foo()
	i.run("hello")
	foo.foo("world")


print "importing foo"
import foo
test()

print "importing bar"
import bar
test()

print "importing baz"
import baz
test()