super().__init__()

https://realpython.com/python-super/

 

 

class Rectangle:

def __init__(self, length, width):

self.length = length

self.width = width

 

def area(self):

return self.length * self.width

 

def perimeter(self):

return 2 * self.length + 2 * self.width

 

class Square:

def __init__(self, length):

self.length = length

 

def area(self):

return self.length * self.length

 

def perimeter(self):

return 4 * self.length

 

a = Rectangle(4, 6)

print("a.area() =", a.area())

print("a.perimeter() =", a.perimeter(), "\n")

b = Square(7)

print("b.area() =", b.area())

print("b.perimeter() =", b.perimeter())

 

 

a.area() = 24

a.perimeter() = 20

 

b.area() = 49

b.perimeter() = 28

 

상속을 사용하면 (1) 코드 줄이면서, (2) 관계를 규정

 

class Rectangle:

def __init__(self, length, width):

self.length = length

self.width = width

 

def area(self):

return self.length * self.width

 

def perimeter(self):

return 2 * self.length + 2 * self.width

 

# Here we declare that the Square class inherits from the Rectangle class

class Square(Rectangle):

def __init__(self, length):

super().__init__(length, length)

 

https://stackoverflow.com/questions/222877/what-does-super-do-in-python

 

The benefits of super() in single-inheritance are minimal -- mostly, you don't have to hard-code the name of the base class into every method that uses its parent methods.

 

However, it's almost impossible to use multiple-inheritance without super(). This includes common idioms like mixins, interfaces, abstract classes, etc. This extends to code that later extends yours. If somebody later wanted to write a class that extended Child and a mixin, their code would not work properly.

Definition. Mixins are a language concept that allows a programmer to inject some code into a class. Mixin programming is a style of software development, in which units of functionality are created in a class and then mixed in with other classes.

 

What's the difference?

 

SomeBaseClass.__init__(self)

means to call SomeBaseClass's __init__. while

 

super(Child, self).__init__()

means to call a bound __init__ from the parent class that follows Child in the instance's Method Resolution Order (MRO).

 

If the instance is a subclass of Child, there may be a different parent that comes next in the MRO.

 

Python 2 versus 3

 

This works in Python 2 and 3:

super(Child, self).__init__()

 

This only works in Python 3:

super().__init__()