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The __init__() method in Python is a default method that is mainly used to initialize the instance variables of a class. For the same reason, it is also referred to as Constructor.

The first parameter of the __init__() method is the self variable containing the memory address of the instance.

Here is the complete tutorial that we have designed for self statement : http://codeofgeeks.com/the-self-variable-in-python-class/

Sample __init__() method is defined as :

def __init__(self):
  self.name = 'Ram'
  self.role = 'God'

In the above code, the constructor __init()__ has only one parameter i.e self. With the help of self.name and self.role, we can access the instance variables of the class.

The __init__() method is called automatically at the time of instance creation. Like,

a = Animal() # Here Animal is our class

Observe the empty parentheses while instantiating a class, this means that we are not passing any values to the constructor at the time of class instantiation.

Let’s try to add some parameters to it now,

a = Animal('meows', 'barks') # Here Animal is our class

The __init__() method to accept the values,

def __init__(self, cat = 'speaks hindi', dog = 'speaks english'):
  self.cat = cat
  self.dog = dog

In this case, we are passing two actual arguments, ‘meows’ and ‘barks’ to the Animal class.

Let’s see the whole code to understand the flow,

class Animal:
  def __init__(self, cat = 'speaks hindi', dog = 'speaks english'):
    self.cat = cat
    self.dog = dog 
  
  def display(self):
    print(self.cat)
    print(self.dog)

a1 = Animal('meows', 'barks') # calling with parameters
a1.display()
a2 = Animal() # calling without parameters
a2.display()

Please note that, even if you don’t write __init__() method inside your class, then too, default constructor will be executed.

class Animal:
  def display(self):
    print('No init here @@')
    
a2 = Animal() # calling without parameters
a2.display()

O/P

No init here @@

Why __init__() method has two trailing and leading underscores ?

Python calls it a special method. This is just a convention, a way for the Python system to use names that won’t conflict with user-defined names. Other examples are __file__, __import__.

That’s all here. Hope, you now know the significance of __init__() method.

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