recursion2.py

def count_change(amount, coins):
    if amount == 0:
        return 1
    if len(coins) == 0 or amount < 0:
        return 0
    return count_change(amount - coins[-1], coins) + \
           count_change(amount, coins[:-1])

results = {}

def factorial(n):
    result = 1
    for i in range(1, n + 1):
        result *= i
    return result

def binom2(n, k):
    return factorial(n) // (factorial(k) * factorial(n - k))

def binom(n, k):
    if (n, k) in results:
        return results[(n, k)]
    
    if k == 0 or k == n:
        return 1
    
    result = binom(n - 1, k - 1) + binom(n - 1, k)
    results[(n, k)] = result
    return result

def foo(a, b, c, *args):
    print(args)
    return a + b + c

class Point:
    def __init__(self, x = 0, y = 0):
        self.x = x
        self.y = y

    def __add__(self, other):
        assert isinstance(other, Point) or isinstance(other, int)
        if isinstance(other, Point):
            return Point(self.x + other.x, self.y + other.y)
        elif isinstance(other, int):
            return Point(self.x + other, self.y)
        else:
            return NotImplemented

    def __radd__(self, other):
        return self + other