Trying to Understand This Line in the Code

Question

I'm kinda new to Python, and just got into Object Oriented. I think I understand the basic but this line of code has really got me confused.

Here's the entire piece:

class SpecialString:
    def __init__(self, cont):
        self.cont = cont

    def __truediv__(self, other):
        line = "=" * len(other.cont)
        return "\n".join([self.cont, line, other.cont])

spam = SpecialString("spam")
hello = SpecialString("Hello world!")
print(spam / hello)

I'm talking about the this one:

line = "=" * len(other.cont)

I don't get what 'other.cont' mean. How can an object be an attribute of another object? Or is 'cont' just being applied on 'other'?

Answer 1

The truediv () special method is only used with the / operator.

Below is how i can breakdown the truediv . This is basically known as operator overloading.

def __truediv__(self, SpecialString("Hello world!")):
    #line = "=" * len(other.cont)
    line = "=" * len(SpecialString("Hello world!").cont)

    #return "\n".join([self.cont, line, other.cont])
    return "\n".join([SpecialString("spam").cont, line, SpecialString("Hello world!").cont])

Other here is the 2nd class instance that is being passed.

There is a question in SO which answers operator overloading of truediv ()in detail. You can check it here: operator overloading for __truediv__ in python

Answer 2

The method expects two object instances as parameters, self and other . The code doesn't care as such which class other belongs to, as long as it has a cont attribute, too, which has a length. But the division method commonly takes two objects of the same type.

(When an object of a different type behaves the same as yours, that's called polymorphism. This isn't crucial to understand at this point, but you've probably come across the concept.)