如何通过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,'-'))