计算Pi到第N位

Question

我正在尝试通过做各种小项目来学习python，在这种情况下，输入一个数字，pi将计算到该数字输入。在谷歌搜索的帮助下，我设法能够计算Pi，但无论我输入的是什么数字，它仍会产生相同数量的Pi数。

我有点困惑，它导致这样做的任何一点，任何提示将非常感谢，提前感谢。这是在python 2.7上

from math import factorial
from decimal import Decimal, getcontext
# Chudnovsky algorithm for figuring out pi
getcontext().prec=100

pi_input = input('How many digits of pi would you like?')
n = int(pi_input)

def calc(n):
    t= Decimal(0)
    pi = Decimal(0)
    deno= Decimal(0)

    for k in range(n):
        t = ((-1)**k)*(factorial(6*k))*(13591409+545140134*k)
        deno = factorial(3*k)*(factorial(k)**3)*(640320**(3*k))
        pi += Decimal(t)/Decimal(deno)
    pi = pi * Decimal(12) / Decimal(640320 ** Decimal(1.5))
    pi = 1/pi
    return pi

print calc(n)

这是我的输出

How many digits of pi would you like? 5 

3.141592653589793238462643383279502884197169399375105820974944592307816346 94690247717268165239156011

Answer 1

使用Chudnovsky算法，计算每次迭代产生大约14.18个十进制数字：log10（（640320 ^ 3）/（24 * 6 * 2 * 6））〜= 14.18。这可以在本网页所示的ak / ak-1公式中更清楚地看到：

https://www.craig-wood.com/nick/articles/pi-chudnovsky

对于n = 5，结果具有大约70位精度。

Answer 2

您可以使用"%.nf"to格式输出字符串，其中n是您要输出的位数。例如

import numpy as np
print "%.5f"%(np.pi)

Answer 3

from math import factorial
from decimal import Decimal, getcontext

n = int(input('How many digits of pi would you like?'))
# Chudnovsky algorithm for figuring out pi
getcontext().prec=n+1
def calc(n):
    t= Decimal(0)
    pi = Decimal(0)
    deno= Decimal(0)
    k=0

    #t = ((-1)**k)*(factorial(6*k))*(13591409+545140134*k)
    t=(1)*(factorial(1))*(13591409+545140134*k)
    deno = factorial(3*k)*(factorial(k)**3)*(640320**(3*k))
    pi += Decimal(t)/Decimal(deno)
    pi = pi * Decimal(12) / Decimal(640320 ** Decimal(1.5))
    pi = 1/pi
    return pi

print (calc(n))

Answer 4

这可能是一个简单的理解代码

from numpy import *

n = int(input('How many digits of pi after decimal would you like to print'))
print(pi)

#print (" value of pi at {:.4f} is" .format(pi))

print('{pi:0.{precision}f}'.format(pi=pi,precision=n))

Answer 5

我就是这样做的:-)

import math
digits = int(input("to how many digits to you want to round PI?"))

def roundpi(n):
    return round(pi,n)

roundpi(digits)