Overloading in Python

 

Python Overloading

Overloading is nothing, but rewriting the two functions with same name and different parameters. 

• Rules to override
• Inheritance is not mandatory

• Method name must be same

• No. of parameters should be different (Must have different signature).

• Python does not support function / method overloading.

• May overload the methods, but can only use the latest defined method 

• Overloading in different class via imheritance

 #program for method overloading in different class via inheritance
 class A :
     def __init__(self):
         print("This is class A constructor")

     def add(self, a, b):
         print("add function of class A")
         return a+b;
 
 class B(A) :
       def add(self, a, b, c):
        print("add function of class B")
        return a-b;

 
 b = B()
 d = b.add(10, 5)
 print("d :", d)

 #Output

 This is class A constructor
 Traceback (most recent call last):
   File "C:/Self_Practice_Er_M_S_Dandyan/Python/Pycharm/xml/main.py", line 10, in <module>
     d = b.add(10, 5)
 TypeError: add() missing 1 required positional argument: 'c'

• Overloading in same class

 #program for method overloading in same class

 class A :
     def __init__(self):
         print("This is class A constructor")

     def add(self, a, b):
         print("add function of class A")
         return a+b;

     def add(self, a, b, c):
         print("add function of class B")
         return a-b;



 b = A()
 d = b.add(10, 5)
 print("d :", d)

 #Output

 This is class A constructor
 Traceback (most recent call last):
   File "C:/Self_Practice_Er_M_S_Dandyan/Python/Pycharm/xml/main.py", line 18, in <module>
     d = b.add(10, 5)
 TypeError: add() missing 1 required positional argument: 'c'

So above in both the cases, call is happening to latest defined function if we have 2 functions with same name, lets reverse function definition and see

 #program 

 class A :
     def __init__(self):
         print("This is class A constructor")

     def add(self, a, b, c):
         print("add function of class A")
         return a+b;

     def add(self, a, b,):
         print("add function of class B")
         return a-b;



 b = A()
 d = b.add(10, 5)
 print("d :", d)

 #Output

 This is class A constructor
 add function of class B
 d : 5

• May overload the function, but can only use the latest defined method

 #program for function overloading

 def add(a, b,):
     print("add function with 2 parameter")
     return a+b;

 def add(a, b, c):
     print("add function with 3 parameter")
     return a-b+c;

 d = add(10, 5)
 print("d :", d)


 #output

 Traceback (most recent call last):
   File "C:/Self_Practice_Er_M_S_Dandyan/Python/Pycharm/xml/main.py", line 11, in <module>
     d = add(10, 5)
 TypeError: add() missing 1 required positional argument: 'c'

Lets try with changing the definition order

 #program for constructor overriding

 def add(a, b, c):
     print("add function with 3 parameter")
     return a+b+c;

 def add(a, b,):
     print("add function with 2 parameter")
     return a-b;

 d = add(10, 5)
 print("d :", d)

 #Output

 add function with 2 parameter
 d : 5

So above example confirms, that we will not get any error of defining function / method as per rules of Overloading, but call will happen to latest defined function / method always