In [6]:
def sum(n):
    pi = 0
    t = 1
    i = 1
    s = 1
    while i < n:
        pi = pi + t
        i = i + 2
        s = -s
        t = s / i
    return pi
n1 = 1000
print (4 * sum(n1))
n2 = 100000
print(4 * sum(n2))


3.139592655589785
3.1415726535897814

In [ ]: