用python计算圆周率PI

def PI(n):
    pi=0
    for k in range(n):
        pi += 1/pow(16,k)*(4/(8*k+1)-2/(8*k+4)-1/(8*k+5)-1/(8*k+6))
    return pi
import time
scale = 20
print("执行开始".center(scale+4,'-'))
for i in range(scale+1):
    a='*' * i
    b='.' * (scale-i)
    c=(i/scale)*100
    pi = PI(1000)
    print("{:^3.0f}%[{}->{}]".format(c,a,b))
    time.sleep(0.1)
print("圆周率值是：{}".format(pi))
print("执行结束".center(scale+4,'-'))