蟒蛇2师

Question

#this works in python 3
def pi_sum(n):
    total, k = 0,1
    while k <= n:
        total, k = total +8 /(k *(k+2)), k + 4
    return total

#this is how i tried to fix it for python 2
def pi_sum2(n):
    total, k = 0,1
    while k <= n:
        total, k = float(total +8) /(k *(k+2)), k + 4
    return total

在 python 2 中：对于pi_sum2(1e6)，我得到8.000032000112001e-12。这里有什么问题？

EDIT 上面我的第一个错误是将浮点数应用于总计和 8.. 我应该做的：

#this is how i tried to fix it for python 2
def pi_sum2(n):
    total, k = 0,1
    while k <= n:
        total, k = total + float(8) /(k *(k+2)), k + 4
    return total

Answer 1

您需要将变量显式定义为浮点数以避免某些类型强制：

def pi_sum(n):
    total, k = 0.0, 1.0
    while k <= n:
        total, k = total + 8.0 /(k *(k+2)), k + 4
    return total

应该做的伎俩