Python Inheritance
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class ParentClass:
# parent members
class ChildClass(ParentClass):
# child members
# super().method_name() calls the parentWhat is Inheritance?
Inheritance lets a child class automatically pick up the attributes and methods of a parent class, so common behavior (like a general Animal.eat() method) only needs to be written once and every subclass (Dog, Cat) gets it for free.
Example: What is Inheritance?
class Animal:
def eat(self):
print("Eating")
class Dog(Animal): # Dog inherits eat() from Animal
pass
Dog().eat()Creating a Subclass
Writing class Dog(Animal): makes Dog a subclass of Animal -- every method and attribute Animal defines becomes available on Dog instances immediately, even before you add anything Dog-specific to its own body.
Example: Creating a Subclass
class Animal:
def eat(self):
print("Eating")
class Dog(Animal): # subclass of Animal
def bark(self):
print("Woof")
d = Dog()
d.eat() # inherited from Animal
d.bark() # defined directly on DogMethod Overriding
If a child class defines a method with the same name as one in its parent, calling that method on a child instance runs the child's version instead -- this is how subclasses customize inherited behavior without touching the parent class at all.
Example: Method Overriding
class Animal:
def speak(self):
print("Some sound")
class Dog(Animal):
def speak(self): # overrides Animal's speak method
print("Woof")
Dog().speak() # runs Dog's version, not Animal'sThe super() Function
super() gives a child class a handle back to its parent, most often used inside __init__ as super().__init__(...) to run the parent's setup logic before adding the child's own attributes, so you don't have to duplicate the parent's initialization code.
Example: The super() Function
class Animal:
def __init__(self, name):
self.name = name
class Dog(Animal):
def __init__(self, name, breed):
super().__init__(name) # runs Animal's __init__ to set self.name
self.breed = breed
d = Dog("Rex", "Labrador")
print(d.name, d.breed)Multiple Inheritance
A single class can list more than one parent -- class Duck(Swimmer, Flyer): -- inheriting from both, which is powerful for combining independent capabilities but requires understanding method resolution order once those parents define overlapping method names.
Example: Multiple Inheritance
class Swimmer:
def swim(self):
print("Swimming")
class Flyer:
def fly(self):
print("Flying")
class Duck(Swimmer, Flyer): # inherits from both parent classes
pass
d = Duck()
d.swim()
d.fly()- Forgetting to call
super().__init__()in a subclass constructor, so the parent's attributes are never set and later access raisesAttributeError. - Overriding a method with a different number of parameters, so code that expects the parent's signature breaks.
- Using inheritance for an "has-a" relationship, such as making
Carinherit fromEngine, instead of storing an engine as an attribute.
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