#Python Polymorphism

The word polymorphism means "many forms", and in programming it refers to methods, functions, or operators with the same name that can be executed on many objects or classes.

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#Function Polymorphism

An example of a Python function that can be used on different objects is the len() function.

#String

For strings, len() returns the number of characters:

pythoncopyx = "Hello World!"
print(len(x))

#Tuple

For tuples, len() returns the number of items in the tuple:

pythoncopymytuple = ("apple", "banana", "cherry")
print(len(mytuple))

#Dictionary

For dictionaries, len() returns the number of key/value pairs in the dictionary:

pythoncopythisdict = {
  "brand": "Ford",
  "model": "Mustang",
  "year": 1964
}
print(len(thisdict))

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#Class Polymorphism

Polymorphism is often used in Class methods, where we can have multiple classes with the same method name. For example, say we have three classes: Car, Boat, and Plane, and they all have a method called move():

pythoncopyclass Car:
  def __init__(self, brand, model):
    self.brand = brand
    self.model = model

  def move(self):
    print("Drive!")

class Boat:
  def __init__(self, brand, model):
    self.brand = brand
    self.model = model

  def move(self):
    print("Sail!")

class Plane:
  def __init__(self, brand, model):
    self.brand = brand
    self.model = model

  def move(self):
    print("Fly!")

car1 = Car("Ford", "Mustang")       # Create a Car object
boat1 = Boat("Ibiza", "Touring 20") # Create a Boat object
plane1 = Plane("Boeing", "747")     # Create a Plane object

for x in (car1, boat1, plane1):
  x.move()

Note: Look at the for loop at the end. Because of polymorphism, we can execute the same method for all three classes regardless of their specific type.

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#Inheritance Class Polymorphism

What about classes with child classes with the same name? Can we use polymorphism there?

Yes. If we make a parent class called Vehicle and make Car, Boat, and Plane child classes, the child classes inherit the Vehicle methods but can override them.

pythoncopyclass Vehicle:
  def __init__(self, brand, model):
    self.brand = brand
    self.model = model

  def move(self):
    print("Move!")

class Car(Vehicle):
  pass

class Boat(Vehicle):
  def move(self):
    print("Sail!")

class Plane(Vehicle):
  def move(self):
    print("Fly!")

car1 = Car("Ford", "Mustang")       # Create a Car object
boat1 = Boat("Ibiza", "Touring 20") # Create a Boat object
plane1 = Plane("Boeing", "747")     # Create a Plane object

for x in (car1, boat1, plane1):
  print(x.brand)
  print(x.model)
  x.move()

• Inheritance: The Car class is empty (pass), but it inherits brand, model, and move() from Vehicle.
• Overriding: The Boat and Plane classes also inherit brand and model, but they override the move() method with their own implementation.

Because of polymorphism, we can execute the same move() method for all classes and get the correct behavior for each specific type.