Lesson 10
I am Your Father
Chapter 2: Inheritance
Inheritance
As discussed in the video, inheritance represents an is-a relation.
- Mammal is a type of animal
- Programming Course is a type of course.
When you inherit from a class, you inherit features from the class and add new features to it. In other words, you add new functionality without modifying the existing code (adhering to the open-closed principle of Software Engineering). You also reuse existing code, obeying the Don’t Repeat Yourself (DRY) principle.
Subclasses and superclasses
If B inherits from A, then B is called the subclass and A is called the superclass. In our example:
Characteris the superclass ofHeroandEnemy.Knightis a subclass ofHero
You can also informally call A the parent class and B the child class.
Everything is an object!
All classes in Python 3 are subclasses of the object class. Everything should output True in the code below.
class Person:
pass
p = Person()
print(issubclass(Person, object))
print(isinstance(p, object))
print(issubclass(int, object))
print(isinstance(3, object))