Question

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python 'self' explained

I am a beginner in Python. I was going through the tutorials on Classes and Iterators when I had a doubt that I was unable to explain to myself. The program text below was a part of a class which calculates area.

def __init__(self,len,wid):
    self.length=len
    self.width=wid

def calculate_area(self)
    return self.length*self.width

def print_area(self)
    print 'Area='+str(self.calculate_area())

What I am unable to understand is why do the function’s argument list have “self”? What is its role? Why are every variable resolved with “self”?

Answer 1

This is similar to this pointer in C++ (if you have come from C++ background)
Typical usage would be that the members of objects can be referenced by self in case if there is an ambiguity. e.g.

def calculate_area(self, length)
    return self.length*self.width

Above length is an argument for calculate_area function.
if the object also has length member then it can be resolved by using self.length

Refer existing answer here:

What is the purpose of self?