What is a Constructor?

• A constructor is a special method (function) used to initialize the class’s instance members.
• The main goal of constructors is to assign values to the class’s data members when an object of the class is created.
• Constructors are always called when an object is created, and the init() method simulates this. It accepts the self-keyword, which refers to itself (the object), as the first argument, allowing access to the class’s attributes or methods.

Syntax:

class class_name:
   def __init__(self):
      # body of the constructor

If you then create an example, the constructor will be called, i.e,

object_1= class_name()

Example:

class Student:

	# default constructor
	def __init__(self):
		self.name = "Rohan Sharma"

	# a method for printing data members
	def print_name(self):
		print(self.name)


# creating object of the class
obj = Student()

# calling the instance method using the object obj
obj.print_name()

Output:

Rohan Sharma

By writing Student() in the code above, we are informing python that obj is an object of class Student. And that is exactly when the constructor of that class is called.

More than One Constructor in a Single class:

The object of the class will always call the last constructor if the class has multiple constructors. For instance,

class Student:  
    def __init__(self):  
        print("The First Constructor")  
    def __init__(self):  
        print("The second contructor")  
  
st = Student()  

Output:

The second contructor

Built-in class attributes:

There are some built-in class attributes that provide information about the class.

Attribute	Description
__dict__	The dictionary containing details about the class namespace is made available.
__doc__	It contains a string that has the class documentation
__name__	It is used to access the class name.
__module__	It is used to access the module in which, this class is defined.
__bases__	It contains a tuple including all base classes.

Note: also read about Python Class

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