How to copy a python class?

In general, inheritance is the right way to go, as the other posters have already pointed out.

However, if you really want to recreate the same type with a different name and without inheritance then you can do it like this:

class B(object):
    x = 3

CopyOfB = type('CopyOfB', B.__bases__, dict(B.__dict__))

b = B()
cob = CopyOfB()

print b.x   # Prints '3'
print cob.x # Prints '3'

b.x = 2
cob.x = 4

print b.x   # Prints '2'
print cob.x # Prints '4'

You have to be careful with mutable attribute values:

class C(object):
    x = []

CopyOfC = type('CopyOfC', C.__bases__, dict(C.__dict__))

c = C()
coc = CopyOfC()

c.x.append(1)
coc.x.append(2)

print c.x   # Prints '[1, 2]' (!)
print coc.x # Prints '[1, 2]' (!)

The right way to "copy" a class, is, as you surmise, inheritance:

class B(A):
    pass

You could use a factory function:

def get_A():
    class A(object):
        ARG = 1
    return A

A = get_A()
B = get_A()