Interest of magic method

Good question! When defining a class, additional methods are needed if you wish to treat the object is special ways, such as comparing or adding them.

Say, I had a Rock class. How would I know if one rock was bigger than another or what a "sum of rocks" equals? It is the magic methods that allow using classes in comparisons or other math statements.

class Rock:
    def __init__(self, size=0):
        self.size = size

One way to compare rocks would be by having a number representation of the rock. Defining an __int__ method says "here is an integer representation of this rock"

    def __int__(self):
        return self.size

Now I can use int() on any Rock instance and get back its size value. To compare this rock to a value

    def __gt__(self, other):
        return int(self) > int(other)

>>> class Rock:
...     def __init__(self, size=0):
...         self.size = size
...     def __int__(self):
...         return self.size
...     def __gt__(self, other):
...         return int(self) > int(other)
...     def __add__(self, other):
...         return int(self) + int(other)
...
>>> r1 = Rock(3)
>>> r2 = Rock(6)
>>> r1 > r2
False
>>> r2 > r1
True
>>> r2 + r1
9

Without these magic methods, comparisons and object math would not be possible.

Post back if you have more questions. Good luck!!