布尔表达式的短路

def func():
    print('HelloWorld!')
x = -2
y = 3
x > 0 or func()
y < 0 or func()

递归需要消耗空间

def A(a, b):
    return B(a+b)
def B(x):
    return C(5, x)
def C(a, b):
    return a * b
print(A(10,20))