cs50p/problems/pset8/jar/jar.py

class Jar:
    def __init__(self, capacity=12):
        if not isinstance(capacity, int) or capacity < 0:
            raise ValueError("Invalid capacity")
        self._capacity = capacity
        self._size = 0

    def __str__(self):
        return '🍪' * self.size

    def deposit(self, n):
        new_size = n + self.size
        if new_size > self.capacity or new_size < 0:
            raise ValueError("Exceeded capacity")
        self._size += n

    def withdraw(self, n):
        return self.deposit(-n)

    @property
    def capacity(self):
        return self._capacity

    @property
    def size(self):
        return self._size