defaultdict_usage.py

from collections import defaultdict
 
class Employee(object):
 
    def __init__(self, first_name, last_name, speciality):
        self._first_name = first_name
        self._last_name = last_name
        self._speciality = speciality
 
 
class Driver(Employee):
    pass
 
# Just defaultdict(Employee) will try to return us an instance of class
# that will cause TypeError: __init__() takes exactly 4 arguments (1 given)
# So we're just returning the class itself.
factory = defaultdict(lambda: Employee)
 
for key in ('x', 'y', 'z'):
    print type(factory[key]('Jimmy', 'Winter', 'engineer'))