Python super() Function

Python3 Built-in Functions

super()It is a built-in function in Python used to call methods of the parent class (superclass).

In class inheritance,super()it allows you to call parent class methods, enabling code reuse and method extension. This is a very important function in Python object-oriented programming.

Word Definition： superIt means "super", referring here to the parent class or superclass.

Basic Syntax and Parameters

Syntax Format

super()
super(type, object-or-type)

Parameter Description

  • Parameter type：
    • Type: class
    • Description: The class for which to obtain the parent class proxy.
  • Parameter object-or-type：
    • Type: object or class
    • Description: Must be an instance or subclass of type.

Function Description

  • Return value: Returns a proxy object used to call methods of the parent class.
  • Feature: Supports Method Resolution Order (MRO) and correctly handles multiple inheritance.

Examples

Example 1: Calling the Parent Class Constructor in a Subclass

Example

# Parent class
class Animal:
    def __init__(self, name):
        self.name = name
        print(f"Animal {self.name} was born")

    def speak(self):
        print("Animal makes a sound")

# Subclass
class Dog(Animal):
    def __init__(self, name, breed):
        # Call the parent class __init__
        super().__init__(name)
        self.breed = breed
        print(f"The breed is {self.breed}")

    def speak(self):
        # Call the parent class method
        super().speak()
        print("Woof!")

# Test
dog = Dog("Little White", "Husky")
# Output:
# Animal Little White was born
# The breed is Husky

dog.speak()
# Output:
# Animal makes a sound
# Woof!

Expected output:

The animal Xiaobai was born
Breed: Husky
The animal makes sounds
Woof woof!

Code analysis:

  1. super().__init__(name)Calls the parent class constructor.
  2. super().speak()Calls the parent class method.
  3. This allows extending the parent class functionality in the subclass.

Example 2: Multiple Inheritance

Example

# Multiple inheritance example
class A:
    def method(self):
        print("A.method")

class B(A):
    def method(self):
        print("B.method")
        super().method()  # Call A.method

class C(A):
    def method(self):
        print("C.method")
        super().method()  # Call A.method

class D(B, C):
    def method(self):
        print("D.method")
        super().method()  # Call in MRO order

# MRO: D -> B -> C -> A
d = D()
d.method()
# Output:
# D.method
# B.method
# C.method
# A.method

# View MRO
print(D.__mro__)

Expected output:

D.method
B.method
C.method
A.method
(<class '__main__.D'>, <class '__main__.B'>, <class '__main__.C'>, <class '__main__.A'>, <class 'object'>)

Code analysis:

  • super()Called according to MRO (Method Resolution Order).
  • This ensures correctness of multiple inheritance.

Example 3: Without Parameters (Recommended)

Example

# Python 3 recommended usage: no parameters needed
class Parent:
    def greet(self, name):
        return f"Hello, {name}!"

class Child(Parent):
    def greet(self, name):
        # Call parent class method and extend
        message = super().greet(name)
        return message + " Welcome back!"

child = Child()
print(child.greet("Tom"))
# Output: Hello, Tom! Welcome back!

Expected output:

Running in an actual environment will display the extended greeting.

super()It is a key function for implementing class inheritance and polymorphism in Python.

Python3 Built-in Functions

Other Extensions