Constructors

A constructor is a special method in a class that runs automatically when an object is created.

In Python, the constructor method is called __init__().

It is used to:

• Initialize object data
• Assign values to attributes
• Set up the object when it is created

BASIC SYNTAX

class ClassName:
    def __init__(self):
        # initialization code

SIMPLE EXAMPLE

class Student:
    def __init__(self):
        print("Constructor is called.")s1 = Student()

When the object s1 is created, the constructor runs automatically.

CONSTRUCTOR WITH PARAMETERS

Most constructors accept parameters to initialize object attributes.

class Student:
    def __init__(self, name, age):
        self.name = name
        self.age = ages1 = Student("Hira", 22)print(s1.name)
print(s1.age)

Explanation:

• __init__ is the constructor
• self refers to the current object
• name and age are object attributes

DEFAULT CONSTRUCTOR

If you do not define a constructor, Python automatically provides a default constructor that does nothing.

class Car:
    passcar1 = Car()

This works even without __init__().

TYPES OF CONSTRUCTORS

1. Default Constructor

No parameters except self.

class Example:
    def __init__(self):
        print("Default constructor")

2. Parameterized Constructor

Accepts arguments.

class Example:
    def __init__(self, value):
        self.value = value

MULTIPLE OBJECTS WITH CONSTRUCTOR

class Car:
    def __init__(self, brand):
        self.brand = brandcar1 = Car("Toyota")
car2 = Car("BMW")print(car1.brand)
print(car2.brand)

Each object has its own data.

IMPORTANT POINTS

• Constructor name must be __init__
• It runs automatically when object is created
• Used to initialize object attributes
• self is required as the first parameter

KEY TAKEAWAY

A constructor initializes the object when it is created.
It helps assign values and prepare the object for use in a clean and structured way.