Code to demonstrate how to create subclasses dynamically when the superclass is not known before execution

dynamic_subclass.py

"""
Code to demonstrate dynamically creating subclasses for a
superclass that is not known before execution.

General idea: you want to make a subclass that is a baby animal,
but you don't know whether it will be a Human or Sheep (or possibly
another animal from a different module) until the code is run.
By creating the subclass dynamically (using the "type" function),
you can avoid writing a separate subclass for each superclass possibility.

Cedric Flamant
"""

class Human():
    def __init__(self, name):
        print("Created Human")
        print(f"My name is {name}")
        self.name = name

    def think(self):
        return "HELLO"

    def speak(self):
        print(self.think())


class Sheep():
    def __init__(self, name):
        print("Created Sheep")
        print(f"Baah baah baah {name}")
        self.name = name

    def think(self):
        return "BAAAAH"

    def speak(self):
        print(self.think())

### Functions for dynamic subclass, Baby ###
def _constructor(self, name):
    super(self.__class__, self).__init__(name)
    print("It's a baby!")

def _babythink(self):
    # make the thought lowercase
    return super(self.__class__, self).think().lower()
##############################################

# Main part of script. Superclasses "Human" and
# "Sheep" are passed at runtime

# make new class BabyHuman dynamically
BabyHuman = type("BabyHuman",
                 (Human,),
                 {"__init__": _constructor,
                  "think": _babythink,
                  })

# make new class BabySheep dynamically
BabySheep = type("BabySheep",
                 (Sheep,),
                 {"__init__": _constructor,
                  "think": _babythink,
                  })

# Construct an adult human
human = Human("Jacob")
human.speak()
# output:
# Created Human
# My name is Jacob
# HELLO

# Construct a baby human
babyhuman = BabyHuman("Timmy")
babyhuman.speak()
# output:
# Created Human
# My name is Timmy
# It's a baby!
# hello

# Construct a baby sheep
babysheep = BabySheep("Woolie")
babysheep.speak()
# output:
# Created Sheep
# Baah baah baah Woolie
# It's a baby!
# baaaah