What is Constructor Overloading in Python? With Examples

Python is a user-friendly programming language that can be easily mastered by beginners. This programming language offers a wide range of community support which helps the programmers in exploring several ways of implementing the code. The standard libraries in Python and the modules contributed by the community forum have allowed endless possibilities, including Web and internet development, desktop GUIs, database access, Education, scientific and numeric applications, network programming, software development and programs to develop games. This open-source language is developed under OSI approved license. Hence, it can be used and distributed free of cost. The Python Software Foundation administers the license of Python.

Constructors in Python:

The main function of a Python constructor is to instantiate the objects. At the time of object creation, the class data members are assigned values or initialized with the help of constructors. The function _init_ is a constructor in Python. It is often called when a new object is created.

The Syntax for declaration of a Constructor is

Def _init_(self):

# constructor’s body

There are two types of constructors in Python. They are:

• Default constructor
• Parameterized constructor

Default constructor:

It is a simple constructor and does not accept any input parameters. The definition of default constructors has only one argument that refers to the instance that is being constructed. 

Parameterized constructor:

As indicated by the name, these constructors have parameters. The first argument of this type of constructors refers to the instance that is constructed and it is known as ‘self’. All other required arguments are specified by the programmer as inputs.

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Constructor Overloading in Python:

Construct overloading refers to a scenario of incorporating more number of constructors with a separate list of parameters such that each constructor is used to accomplish different tasks in the program. For example, there are four types of constructors in the Vector class. 

Python does not explicitly support multiple constructors. However, the use of multiple constructors in Python can be accomplished in several ways. If a programmer writes multiple _init_ methods for the same class, the most recently written _init_ function overwrites all other constructors.

Why are Multiple constructors required in Python?

When the user has a need of performing different actions to instantiate a class, the requirement of multiple constructors pops up. This is helpful when different actions are to be performed by the class on different parameters. The class constructors in Python are structured to exhibit polymorphism in three different ways, as listed below:

1. Constructor overloading based on arguments
2. Invoking _init_ methods
3. Use of the @classmethod decorator

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Constructor Overloading in Python based on Arguments:

In this method, the constructors are overloaded by performing necessary action after the conditions for the passed arguments are checked. Let us consider an example of passing a parameter to the Sample class.

• The number’s square is the answer if the input parameter is an int. 
• If the length of the parameter is more than 1, the arguments’ sum is shown as the answer. 

Calling Methods with _init_:

When an instance of a class is created, the class can have a single _init_ constructor that can perform any assigned task. This constructor can be modified to handle different functions and perform different tasks based on the parameter that is passed. Let us consider an example where the following calculations are performed.

• If two arguments are passed, the expression is evaluated as x = a2 – b2 
• If three arguments are passed, then the expression evaluated is y = a2 + b2 – c
• If the number of arguments passed exceeds three, then add the squares of those numbers and divide the sum by the argument with the highest value.

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