The Python self variable trouble !

Hi there fellas. In this post I am going to teach you about the self variable in python. I have seen many beginners struggling to grasp the concept of self variable. If you are one of them then this post is for you. So lets start by making a class involving the self variable.

class Restaurant(object):
bankrupt = False
def open_branch(self):
if not self.bankrupt:
print("branch opened")
x = Restaurant()
x.bankrupt
Restaurant().bankrupt

>>> x = Restaurant()
>>> x.bankrupt
False

>>> y = Restaurant()
>>> y.bankrupt = True
>>> y.bankrupt
True

>>> x.bankrupt
False

class Restaurant(object):
bankrupt = False
def open_branch(this):
if not this.bankrupt:
print("branch opened")

A simple class :So here is our class:

First let me explain the above code without the technicalities. First of all we make a class Restaurant. Then we assign it a property “bankrupt” which is currently false. After that we assign it a function open_branch which can only occur if “bankrupt” is False which means that the Restaurant has some money.

Making a resturant:

Now that we have made a class for a Restaurant, lets actually make a resturant:

Now x is a Restaurant which has a property bankrupt and a function open_branch. Now we can access the property bankrupt by typing:

The above command is same as:

Now you can see that self refers to the bound variable or object. In the first case it was x because we had assigned the Restaurant class to x whereas in the second case it referred to Restaurant(). Now if we have another Restaurant y, self will know to access the bankrupt value of y and not x. For example check this example:

The first argument of every class method, including __init__, is always a reference to the current instance of the class. By convention, this argument is always named self. In the __init__ method, self refers to the newly created object; in other class methods, it refers to the instance whose method was called. For example the below code is the same as the above code.

Free Tip:

However self is not a reserved keyword in python it’s just a strong convention. Many people say that why do we have to write self ? Why can’t we have it set automatically like in Java ? Someone also filed a PEP (improvement suggestion) in which he suggested to remove the explicit assignment of self keyword. However Guido Van Rossum (the maker of python) wrote a blogpost in which he told why explicit self has to stay.