Math.pi вывести число определенной длинны (с определенной точностью)

import sys
import math
from decimal import *
from math import factorial
from time import time
 
# http://thelivingpearl.com/2013/05/28/computing-pi-with-python/
# http://www.numberworld.org/misc_runs/pi-5t/details.html
 
# Bellard's Formula PI
 
 
def bellard(n):
    pi = Decimal(0)
    k = 0
    while k < n:
      pi += (Decimal(-1)**k / (1024**k)) * (Decimal(256) / (10 * k + 1) + Decimal(1) / (10 * k + 9) - Decimal(64) / (10 * k + 3) - Decimal(32) / (4 * k + 1) - Decimal(4) / (10 * k + 5) - Decimal(4) / (10 * k + 7) - Decimal(1) / (4 * k + 3))
      k += 1
    pi = pi * 1 / (2**6)
    return pi
 
# Bailey-Borwein-Plouffe formula
 
 
def bbp(n):
    pi = Decimal(0)
    k = 0
    while k < n:
        pi += (Decimal(1) / (16**k)) * ((Decimal(4) / (8 * k + 1)) - (Decimal(2) / (8 * k + 4)) - (Decimal(1) / (8 * k + 5)) - (Decimal(1) / (8 * k + 6)))
        k += 1
    return pi
 
# http://www.craig-wood.com/nick/articles/pi-chudnovsky/
 
 
def chudnovsky(n):
    pi = Decimal(0)
    k = 0
    while k < n:
        pi += (Decimal(-1)**k) * (Decimal(factorial(6 * k)) / ((factorial(k)**3) * (factorial(3 * k))) * (13591409 + 545140134 * k) / (640320**(3 * k)))
        k += 1
    pi = pi * Decimal(10005).sqrt() / 4270934400
    pi = pi**(-1)
    return pi
 
 
def chudnovsky2(n):
    pi = Decimal(13591409)
    ak = Decimal(1)
    k = 1
    while k < n:
        ak *= -Decimal((6 * k - 5) * (2 * k - 1) * (6 * k - 1)) / Decimal(k * k * k * 26680 * 640320 * 640320)
 
        val = ak * (13591409 + 545140134 * k)
 
        d = Decimal((6 * k - 5) * (2 * k - 1) * (6 * k - 1)) / Decimal(k * k * k * 26680 * 640320 * 640320)
 
        pi += val
        k += 1
    pi = pi * Decimal(10005).sqrt() / 4270934400
    pi = pi**(-1)
    return pi
 
# arctan
# http://www.craig-wood.com/nick/articles/pi-machin/
 
 
def arctan(x):
    """
    Calculate arctan(1/x)
 
    arctan(1/x) = 1/x - 1/3*x**3 + 1/5*x**5 - ... (x >= 1)
 
    This calculates it in fixed point, using the value for one passed in
    """
    x2 = x * x
    x = Decimal(x)
 
    total = Decimal(0)
    sign = 1
    for i in range(1, 512, 2):
        #total += sign / (i * x)
        total += sign / (i * x ** i)
        sign = -sign
        #x *= x2
        # print(total)
    return total
 
 
def pi_machin(n):
    return 4 * (4 * arctan(5) - arctan(239))
 
 
def pi_gauss(one):
    return 4 * (12 * arctan(18) + 8 * arctan(57) - 5 * arctan(239))
 
 
if __name__ == "__main__":
 
    N = 1000
  
    getcontext().prec = N
  
    print ""
    print "Atan"
    start = time()
    my_pi = pi_machin(N)
    print "Pi = {}".format(str(my_pi))
    print("Time", time() - start)
  
    print "BBP"
    start = time()
    my_pi = bbp(N)
    print "Pi = {}".format(str(my_pi))
    print("Time", time() - start)
  
    print "Bellard"
    start = time()
    my_pi = bellard(N)
    print "Pi = {}".format(str(my_pi))
    print("Time", time() - start)
  
    print ""
    print "Chudnovsky"
    start = time()
    my_pi = chudnovsky(N / 14)
    print "Pi = {}".format(str(my_pi))
    print("Time", time() - start)
  
    print ""
    print "Chudnovsky2"
    start = time()
    my_pi = chudnovsky2(N / 14)
    print "Pi = {}".format(str(my_pi))
    print("Time", time() - start)