__init__() function

• This is a function which we do not need to call.
• If we define this function in the class then it is the first function in the life of an object which is called.
• When we create an object of the class in which this function is defined then this function is called automatically for that object.
• Mainly this function is used to define instance members of the object.
• If you have knowledge of java or c++ language, then you can say that this function is just similar to constructor.

**One argument is necessary in __init__ function while we define it.
When an object call this function object itself is passed as a first argument.
class square:
    def __init__(self,side): 
        self.side=side
    def calarea(self):
        x=self.side
        print("The area of square is ",x*x)
        
s1=square(10)
s2=square(20)
s1.calarea()

Output:
The area of square is  100
The area of square is  400

Example2: Write an script to calculate the area of rectangle whose length and breadth are taken from the user in object oriented way.
class rect:
    def __init__(self,l,b):
        self.l=l
        self.b=b
    def calarea(self):
        x=self.l
        y=self.b
        print("The area of rectangle is",x*y)

a,b=int(input("Enter length ")),int(input("Enter breadth "))
r1=rect(a,b)
r1.calarea()

Output:

Enter length 3

Enter breadth 4

The area of rectangle is 12