Polymorphism

An object can take many (poly) forms (morph)

Case 1

1. The same method in a class works in a similar way for different classes
   • Common implementation is to have a method in a base (or a parent) class that is overridden by a subclass → method overriding

class Animal():
	def speak(self):
		raise NotImplementedError("Subclass needs to override this!")
 
class Cat(Animal):
	def speak(self):
		return "meow"
 
class Dog(Animal):
	def speak(self):
		return "woof"
 
Cat.speak() # meow
Dog.speak() # woof

Case 2

2. Special/dunder/magic methods
   • Magic methods are special methods that define how objects behave with Python’s built-in operations (like +, len(), ==, etc.).
   • They allow you to define behavior for built-in operations in Python, like arithmetic operations, comparisons, and more
     • Ex) when you use + to add two objects, Python internally calls the __add__() method on those objects
   • Same method behaves differently depending on which object(s) it’s working with

A = (1,2)
B = [1,2]
len(A)
len(B)
# A and B's data types are different, but len can be used!

• You can declare special methods on your own classes to mimic the behavior of builtin objects, such as __len__ or __add__

class Human:
	def __init__(self, height):
		self.height = height # in inches
		
	def __len__(self):
		return self.height
		
	def __repr__(self):
		return f"Human {self.name}"
 
Tim = Human(150)
len(Tim) # 150
print(Tim) # Human Tim