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Python Object-Oriented Python (retired) Objects Create a Class with a Method

Posted by Adam Marasli-Zaade
Adam Marasli-Zaade
2,966 Points

I solved it but I have not understood yet why I have to use the argument of the method in the format function?

Why I can't use the name of the variables I have given about the opening and the closing hours?

method.py 
class Store:
    open = 10
    close = 18

    def hours(hour):
        return "We're open from {} to {}.".format(hour.open, hour.close)

That's the solution.

Adam Marasli-Zaade
Adam Marasli-Zaade
2,966 Points 
class Store:
    open = 10
    close = 18

    def hours(hour):
        return "We're open from {} to {}.".format(open, close)

That's what I mean.

1 Answer

Garrett Guevara
Garrett Guevara
11,331 Points

Hi Adam,

The reason is a difficult one to understand, but it's part of how Python handles inheritance. A regular function can operate on its own; but for a method, which is a child of its parent class, it has to be "aware" of its parent to function. To do this, we pass the method the reference "self" by convention.

There's a great explanation as to why we use "self" on stack overflow that will probably explain it better than I can:

http://stackoverflow.com/questions/2709821/what-is-the-purpose-of-self

So typically, your answer would probably look more like:

class Store():
    open = 10
    close = 18

    def hours(self):
        return "We're open from {} to {}.".format(self.open, self.close)

Hope this helps and good luck!