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Constructors in Python [Guide]

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22nd Jun, 2023
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Constructors in Python [Guide]

Python is one of the most popular programming languages in the contemporary world. Every instance in this programming language is created on an object and hence this is an object-oriented programming language. A Special type of function or method that is used to initialize the instances of distinguished entities of the class are called Python Constructors.

There are two types of Python constructors, namely parameterized and non-parameterized constructors.

Non-parameterized Constructor: These constructors of Python do not have any parameters involved at the time of creation. Non-parameterized constructors are also referred to as default constructors. The parameters are by default obtained from the object that is created for a respective class.

Parameterized Constructor: These constructors have predefined parameters included at the time of creation.

Once the object is created within a class, the constructor is defined in the Python code. The Constructor also ensures that there is enough resource to initiate the execution of code within the object enclosed by a class.

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Python Constructor Creation

It is a must to use the _init_ function or method to create a Python constructor. This method should be invoked immediately after the initialization of the class. Any number of parameters can be passed while creating objects of a class as per your needs after defining and invoking the _init_ method. Constructor is mainly used for initializing the class attributes. A constructor is a must for the functioning of every class created in Python. The code below shows an example of using constructors. 

Python Constructor Creation

The output of the above program may look as shown below.

ID: 101

Name: John

ID: 102

Name: David

Python’s Class Constructors and the Instantiation Process

Python allows for the use of constructors to create objects from a class. A Python constructor is a unique method called/invoked when an object is instantiated from its corresponding class. The constructor method has a similar name as the class, and it’s used to assign initial values to attributes or perform any other setup tasks that need to be done for objects of that particular type. It can also take parameters if we want to customize certain aspects of each object created with it.

By default, Python provides a single no-argument constructor which just creates the instance without doing anything extra apart from assigning memory and setting all attributes to their default value (if declared). This type of constructor is not very useful in most cases, so instead, developers usually define custom constructors that take arguments and use them to set the initial values of the particular attributes. This is known as Python constructor overload.

Constructor overloading in Python makes it possible to pass different numbers of arguments to the same constructor and have it create objects with different attribute values based on those arguments. It is also an important mechanism for creating custom classes in Python. For instance, developers can define a custom constructor which takes different parameters depending on what type of object they are trying to create and then use this information to set up all relevant attributes automatically.

In summary, Python’s class constructors are useful tools for creating and setting up objects from a given class. By defining custom constructors with argument overloads, developers can customize various aspects of the objects they create. This makes it much easier to manage attributes and ensure that all objects have an appropriate set of values when they are first instantiated.

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Distinction of Parameterized and Non-Parameterized Constructor

The main difference between parameterized and non-parameterized constructors is that the parameterized constructor embraces a predefined value, whereas non-parameterized constructor do not have any assigned values. The usage of parameterized and non-parameterized constructors vary with the context and program requirement. 

Figure 1 Example for a Python Code with Non-Parameterized Construct

Figure 2 Example of Python code with Parameterized Construct

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Working of a Constructor

The first code statement of the Python code when an object is developed for a Python class. This code statement initiates the object and initializes the execution of an object. The working of constructors mainly lies within two key elements. They are:

  1. _Init_() function
  2. Self-reference

Init() function

When the instance of an object for the associated class is created, this function is invoked. Just like any other function declarations, the affirmation of the Init() function is also done with a ‘def’ keyword. Do not forget to use underscores as a prefix and suffix while declaring the init() function. An example of usage of the init() function in Python code is shown below.

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Self Reference

The Self reference indicates the involvement of the object itself. The functions and parameters of the class to which the object belongs are used for the initialization of the object. The first parameter of the declaration of the content should mention ‘self’. This is to indicate that the exponent should work with the particular object’s attributes. The code fragment given below shows the usage of ‘self’ reference as Python Constructors.

Benefits and features of Constructors in Python

  • One of the crucial benefits of constructors is that they can be used to initialize the objects.
  • Only constructors can set or initialize variables of an instance at final status.
  • The use of constructors can omit the initialization of default values.
  • The first code statement to be triggered for execution when an object is developed with a class in Python is the constructor. All other initializations are made by the initialization of the constructor. 
  • Initialization of constructors is possible even when there are no predefined arguments or parameters.

Drawbacks of Using Python’s Class Constructors 

  1. One of the main drawbacks of using Python’s class constructor is constructor overloading in Python. This means, unlike other programming languages such as Java and C++, you cannot create multiple constructors with different sets of parameters. Without this feature, when creating a new object, it can become difficult to modify or manipulate it in certain ways due to Python constructor overload
  2. Another drawback is that while classes are generally well-structured blocks of code when using Python’s class constructor, there is no way to enforce type safety on objects created using the constructor. This can lead to unexpected errors and bugs if an improperly structured object is used down the line in your program.
  3. Finally, if you decide to use a constructor in Python, the code can quickly become cluttered with all the different types and parameters that must be defined. This can lead to a decrease in code readability and make it difficult for other developers working on your project to understand what is happening.

Overall, while using Python constructors may have some benefits, they should be used carefully and sparingly due to their lack of support for overloads, type safety enforcement, and readability. If these drawbacks outweigh the potential benefits of using a constructor, then it may be best to avoid them altogether.

Constructors have a major role to play in all high-level programming languages. Object-oriented programming languages utilize constructors as the primary constituents of their code. An enhanced initialization of variables of an instance can be accomplished with the use of constructors. Hence, it is important for a Python programmer to master the usage of constructors in a program.

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Rohit Sharma

Blog Author
Rohit Sharma is the Program Director for the UpGrad-IIIT Bangalore, PG Diploma Data Analytics Program.

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