super（）。method（）和self.method（）有什么区别

Question

What's the difference between using super().method() and self.method() , when we inherit something from a parent class and why use one instead of another?

The only thing that comes to my mind is that with static methods it becomes obviously impossible to call self.method() . As for everything else I can't come up with justification to use super() .

Could someone present a dummy example when choosing one over another matters and explain why, or is it just convention thing?

Answer 1

super().method() will call the parent classes implementation of method , even if the child has defined their own. You can read the documentation for super for a more in-depth explanation.

class Parent:
    def foo(self):
        print("Parent implementation")

class Child(Parent):
    def foo(self):
        print("Child implementation")
    def parent(self):
        super().foo()
    def child(self):
        self.foo()

c = Child()
c.parent()
# Parent implementation
c.child()
# Child implementation

For singular-inheritance classes like Child , super().foo() is the same as the more explicit Parent.foo(self) . In cases of multiple inheritance, super will determine which foo definition to use based on the Method Resolution Order, or MRO .

A further motivating example: which method gets called if we subclass Child and write another implementation of foo ?

class Grandchild(Child):
    def foo(self):
        print("Grandchild implementation")

g = Grandchild()
g.parent()
# Parent implementation
g.child()
# Grandchild implementation

Answer 2

self

self , which is mostly used as the first parameter of instance methods of classes, always represents the calling object/instance of the class.

super()

super() refers to object of parent class. It is useful in case of method overriding and this is in case of numerous programming languages including C++, Java etc. In Java, super() is used to call the constructor of parent class.

Please have a look at the below little example.

class TopClass(object):
    def __init__(self, name, age):
        self.name = name;
        self.age = age;

    def print_details(self):
        print("Details:-")
        print("Name: ", self.name)
        print("Age: ", self.age)
        self.method()

    def method(self):
        print("Inside method of TopClass")

class BottomClass(TopClass):
    def method(self):
        print("Inside method of BottomClass")    

    def self_caller(self):
         self.method()

    def super_caller(self):
         parent = super()
         print(parent)
         parent.method()

child = BottomClass ("Ryan Holding", 26)
child.print_details()

"""
Details:-
Name:  Ryan Holding
Age:  26
Inside method of BottomClass
"""

parent = TopClass("Rishikesh Agrawani", 26)
parent.print_details()

"""
Details:-
Name:  Rishikesh Agrawani
Age:  26
Inside method of TopClass
"""

child.self_caller()
child.super_caller()

"""
Inside method of BottomClass
<super: <class 'BottomClass'>, <BottomClass object>>
Inside method of TopClass
"""