Test python import

a.py

print "defining A"
class A(object):
  def __init__():
    print 'A'

b.py

from a import A

print "defining B"
class B(A):
  def __init__():
    print 'B'

    
import c

c.py

from a import A

print "defining C"
class C(A):
  def __init__():
    print 'C'

test.py

from a import A

print A.__subclasses__()
# []

import b
# defining B
# defining C

print A.__subclasses__()
# [<class 'b.B'>, <class 'c.C'>]