Create class instance on-the-fly with Python

gistfile1.py

>>> class Dog(object):
...     pass
... 
>>> class Cat(object):
...     pass
... 
>>> def create_object(class_name):
...     return getattr(__import__(__name__), class_name)()
... 
>>> dog = create_object('Dog')
>>> dog
<__main__.Dog object at 0x1d9ac50>
>>> cat = create_object('Cat')
>>> cat
<__main__.Cat object at 0x1d9ab50>

Replace name with the name of the module where classes are defined.