Methods and state

Objects that change over time

The point of an object is that it remembers things between calls:

class Basket:
    def __init__(self):
        self.items = []

    def add(self, item):
        self.items.append(item)

    def count(self):
        return len(self.items)

Note self.items = [] inside __init__ rather than at the class level. A list defined directly in the class body is shared by every instance — the same trap as a mutable default argument, in a different costume.

Your turn: write a Basket class with add(item), remove(item) (which ignores items that are not there), and total() returning how many items it holds.