Polymorphism is one of the principles of Object Oriented Programming (OOP). Polymorphism is when an object is able to have more than one form. For example, we can have the same method but in the different classes like so:

class Child:    
    def walk():
        print('Child is walking')

class Adult:
    def walk():
        print('Adult is walking')

We can then create objects and call these same methods irrespective of the class and the output will be different:

person1 = Child()
person2 = Adult()