pi.py

import math
from decimal import *

import numpy as np



def getp(prec=1000, v=True):
    
    prec = prec+2
    N = 2*math.ceil(math.log2(prec)) 

    getcontext().prec = prec 

    a = Decimal(1.0)
    b = Decimal(1.0) / Decimal(2.0).sqrt()
    t = Decimal(0.25)
    p = Decimal(1.0)



    # N回
    for _ in range(1, N):
        a_next = (a + b)/Decimal(2)
        b_next = (a*b).sqrt()
        t_next = t - p * (a - a_next)**2
        p_next = Decimal(2)*p

        a = a_next
        b = b_next
        t = t_next
        p = p_next

    #円周率
    pi = (a + b)**2 / (Decimal(4)*t)
   

    if v:
        print("桁：",prec)
        print("円周率:", pi)

    return str(pi)[0:prec]
    
pi = getp(prec=1000, v=True)

pipy.py

import math
from decimal import *


prec=1000
    
N = 2*math.ceil(math.log2(prec)) 

getcontext().prec = prec 

a = Decimal(1.0)
b = Decimal(1.0) / Decimal(2.0).sqrt()
t = Decimal(0.25)
p = Decimal(1.0)



    # N回の試行を開始
for _ in range(1, N):
    a2 = (a + b)/Decimal(2)
    b2 = (a*b).sqrt()
    t2 = t - p * (a - a2)**2
    p2 = Decimal(2)*p

    a = a2
    b = b2
    t = t2
    p = p2

    #円周率
pi = (a + b)**2 / (Decimal(4)*t)
    #実行時間を計算

    #結果

print("桁：",prec)
print("円周率:", pi)
    
str(pi)[0:prec]