Python 3: self vs __init__

Self represents the instance of the class, used to access the attributes and methods of the class.

init is a reserved method in classes. This constructor allows us to initialize values of the class. Furthermore, with init we can initialize multiple instances of a class that are effectively decoupled.

Here’s an example in python:

class testClass(): 
    x = 123
    def __init__(self):
        self.x = 456

Let’s look at some cases:

#Case a: get the attribute x of the class testClass()
#For case a we get 123 as the value as we are not instantiating the class
a = testClass.x
print('The attribute x of testClass is: {}'.format(str(a)))

The attribute x of testClass is 123

#Case b: instantiate testClass and get the attribute x
#For case b we get 456 as the value as the act of instantiating the class utilizes the init method

b = testClass()
print('The attribute x of an instantiated testClass() is: {}'.format(str(b.x)))

The attribute x of an instantiated testClass() is 456

#Case c: instantiate testClass, pass a value, and get the attribute x
c = testClass()
c.x = 789
print('The attribute x with a value passed is: {}'.format(str(c.x)))

The attribute x with a value passed is 789