Optimal Statements in Python

[DeaD_EyE]

The methods are called Magic Methods or Dunder Methods (double under).
This methods are called by types:

int()
float()
bool()
len()
list()
... and more

If you want to implement a special behaviour of an object, you use the dunder methods for it.
For example you have a class with for a card deck. You can implement the method __len__ to return the amout of cards:

class Deck:
    def __init__(self, cards):
        self.cards = cards
    def __len__(self):
        return len(self.cards)


# then make an instance of the class
cards = Deck([1,2,3])

# then use the len function
print(len(cards))

len(object) calls object.__len__() in a high level view.


Pro Tip: Look for iter() and __iter__
If you implement this method, your Object supports iteration.
The iterator protocol is one of most powerful features in Python.