A Complete Guide To Method Overloading in Python (With examples)

Overloading is the ability of a function, method, or operator to work differently when you pass different parameters to the same. Method overloading or Function overloading in Python have commonly used terms. Some of the main advantages of overloading is that you can use one method in multiple ways, which helps you keep your code cleaner and removes complexity when working with a team.

What is Method Overloading?

In Object-Oriented Programming, Method Overloading is used in scenarios where, for a specific object, a particular method can be called in more than one way according to the project requirement.

Examples of Method Overloading in Python are discussed in detail later in the article.

 What is Method Overriding?

Method Overriding in Python is similar to Method Overloading except for that method overriding occurs between a subclass and a superclass. It has the same parameters as to when the methods are called. Yet, they behave differently due to some of the functionality being overridden from the superclass.

Example of Method Overriding

class X:

    def method1(self):
        print(‘I’m the first feature of class X’)
    def method2(self):
        print(‘I’m the second feature of class X’)
class Y(X):
    def method1(self):
        print(‘I’m the modified first feature of class X in class Y’)   
    def method3(self):
        print(‘I’m a feature of class Y’)
obj = Y()
obj.method1()
Output:

I’m the modified first feature of class X in class Y

method1 was overridden by class Y.

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Method Overloading in Python

The problem with method overloading in Python is that Python does not support it by default. However, there are workarounds to do the same.

The Problem

Let us consider the following code:

def add(a, b):
s = a + b
print(s)
def add(a, b, c):
s = a + b + c
print(s)
# add(8, 9) shows error
add(8, 9, 2)

At first glance, the code looks good, but when you try to execute it with two arguments, Python will show you an error because in Python, when you have more than one method of the same name but a different number of arguments, only the latest defined method can be used. 

There are two different ways we can overcome this problem of method overloading in Python.

1: Using the same methods differ according to the data type of the arguments

We can see an argument to know the data type, along with *args that allows passing a variable number of arguments to a method in Python. We can then use if statements to control how the method behaves according to the input.

CODE: 

def add(dt, *args):
if dt ==’int’:
s = 0
if dt ==’str’:
s = ”
for x in args:
s = s + x
print(s)
add(‘int’, 11, 9)
add(“str”, “Hello,”, “How are you?”)
Output:

20

Hello, How are you?

This was the first workaround to implement method overloading in Python.

2: Using Multiple Dispatch Decorator (More efficient way)

Multiple Dispatch Decorator is less of a workaround and works exactly like it is supposed to. You can install it using pip3.

pip3 install multiple dispatches

CODE:
from multiple dispatch import dispatch
@dispatch(int,int) # for 2 integer arguments
def add(n1,n2):
    s = n1 + n2
    print(s) 
@dispatch(int,int,int) # for 3 integer arguments
def add(n1,n2,n3):
    s = n1 + n2 + n3
    print(s)
@dispatch(float,float,float) # for float arguments
def add(n1,n2,n3):
    s = n1 + n2 + n3
    print(s  
add(5,2)
add(6,1,4) 
add(3.4,1.2,5.6) 
Output:
7
11
10.2

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When executing, the dispatcher makes a new object that stores different implementations of the method and decides the method to select depending on the type and number of arguments passed while calling the method. This way method of overloading in Python is more efficient.

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