Role Of super() in Python🤔

 

SUPER()

The super() builtin returns a proxy object (temporary object of the superclass) that allows us to access methods and other properties of the base class.

 Example 1 :

class Person:
    def __init__(self,name,age):
      self.name = name
      self.age = age
class Student(Person):
    def __init__(self,name,age,grade):
      super().__init__(name,age)
      self.grade = grade
    def printGrade(self):
      print('Student name is {} age is{}Grade is{}.format(self.name,self.age,self.grade))
stud1 = Student('tom',24,'A')
stud1.printGrade()
>> Student name is tom age is 24 and Grade is A

From the above program, we can see that we have used the instances of the parent class in the child class using the super keyword, like this we can also call methods that defined inside the parent class into child class.

Example 2 :

From above example we can conclude that we can access all Instance variables and methods inside child class Instance method with the help of super().

Things to be remembered while using super()

1. Child class --> not allowed to access instance variables(parent class) by using super()

Example

class Parent:

    def __init__(self):

        self.city='Chennai'

class Child(Parent):

        super().__init__()  

        print(self.city)

>> AttributeError: 'super' object has no arguments

Error raised because we cannot access instance variable and instance method/ constructor of parent class inside child class. To avoid this we need to use super inside child class instance method/constructor.

class Parent:

    def __init__(self):

        self.city='Chennai'

class Child(Parent):

    def __init__(self):

        super().__init__()  

        print(self.city)

c1 = Child()

>> Chennai  # now the error is resolved

2. child class constructor and instance method --> access instance, class, static methods

Example

class Parent:

  def __init__(self):

    print('parent constructor')

  def m1(self):

    print('parent instancemethod')

  @classmethod

  def m2(cls):

    print('Parent classmethod')

  @staticmethod

  def m3():

    print('Parent staticmethod')

class Child(Parent):

  def __init__(self): # Child class constructor

    super().__init__()

    super().m1()

    super().m2()

    super().m3()

  

  def m4(self): # Child class Instance method

    super().__init__()

    super().m1()

    super().m2()

    super().m3()

a = Child()

>>

parent constructor parent instancemethod Parent classmethod Parent staticmethod

a . m4()

>>

parent constructor parent instancemethod Parent classmethod Parent staticmethod

3. child class, class method --> cannot access parent class instance methods and constructors by using super() directly . But by indirect means we can access it.

class Parent:

  def __init__(self):

    print('parent constructor')

  def m1(self):

    print('parent instancemethod')

  @classmethod

  def m2(cls):

    print('Parent classmethod')

  @staticmethod

  def m3():

    print('Parent staticmethod')

class Child(Parent): 

@classmethod

  def m5(cls):

    super().__init__() #constructor

    super().m1() # instance method

    super().m2()

    super().m3()

a = child()

a.m5()

>> TypeError: __init__() missing 1 required positional argument: 'self'

class Child(Parent): 

@classmethod

  def m5(cls):

    super(Child,cls).__init__(cls) #constructor

    super(Child,cls).m1(cls) # instance method

    super().m2()

    super().m3()

a = Child()

a . m5()

>>

parent constructor parent instancemethod Parent classmethod Parent staticmethod

Thus by calling indirectly we can access instance method/constructor of parent

class inside child class, class method .

4. Child class static method --> we cannot access parent class instance methods and constructors by using super() both by directly or indirectly.

class Parent:

  def __init__(self):

    print('parent constructor')

  def m1(self):

    print('parent instancemethod')

  @classmethod

  def m2(cls):

    print('Parent classmethod')

  @staticmethod

  def m3():

    print('Parent staticmethod')

class Child(Parent): 

@staticmethod

  def m5(cls):

        super(Child,Child).__init__() #constructor

        super(Child,Child).m1() # instance method

        super().m2()

        super().m3()

a = child()

a.m6()

>> TypeError: __init__() missing 1 required positional argument: 'self'

Thus we cannot access instance method/constructor of parent class inside static method of child class directly or indirectly.

Only static and class methods of parent can be access inside child class static method

class Child(Parent): 

@staticmethod

  def m5(cls):

        super().m2()

        super().m3()

a = child()

a.m6()

>>

Parent classmethod Parent staticmethod