11.4.2.1 explain the concept of polymorphism with examples

Python. Polymorphism

Polymorphism - different behavior of the same method in different classes.

Polymorphism is defined by a function that can process data of different types.

The property of code to work with different data types is called polymorphism.

Examples

One example is the function len().

We can define the length of string, list, tuple, etc.

print(len('school'))  # 6
print(len([2, 3, 5, 7, 11, 13, 17, 19, 23]))  # 9
print(len(('A', 'B', 'C')))  # 3

Other example, operation + (addition). In Python we can add whole numbers, float numbers, strings, lists, etc.

print(5 + 3)                    # 8
print(2.7 + 3.4)                # 6.1
print('Hello, ' + 'world!')     # Hello, world!
print([2, 3, 5] + [7, 11, 13])  # [2, 3, 5, 7, 11, 13]

Use addition function

def func_add(x, y):
    return x + y

print(func_add(5, 3))                    # 8
print(func_add(2.7, 3.4))                # 6.1
print(func_add('Hello, ', 'world!'))     # Hello, world!
print(func_add([2, 3, 5], [7, 11, 13]))  # [2, 3, 5, 7, 11, 13]

All function calls work correctly because Python is a dynamically typed language. The interpreter chooses the correct implementation of the operation +.

Consider an example of programming code that contains two classes: Circle() and Square(). Each class has methods for measuring area and perimeter.

from math import pi
class Circle:
    def __init__(self, radius): # initialize one attribute radius
        self.radius = radius
  
    def area(self):
        return pi * self.radius ** 2
 
    def perimeter(self):
        return 2 * pi * self.radius
 
class Square:
    def __init__(self, side): # initialize one attribute side
        self.side = side
 
    def area(self):
        return self.side * self.side
 
    def perimeter(self):
        return 4 * self.side
    
def print_shape_info(shape): # polymorphic function for displaying the area and perimeter of a shape
    print(f"Area = {shape.area()}, perimeter = {shape.perimeter()}.")

# create an instance square
square = Square(2)
print_shape_info(square)   # Area = 4, perimeter = 8.
# create an instance circle
circle = Circle(5)
print_shape_info(circle)     # Area = 78.53981633974483, perimeter = 31.41592653589793.

Questions:

1. Explain the term "polymorphism".
2. Give an example of polymorphism in real life.
3. How to find out by the class name what methods it implements?

Exercises:

Tasks: