python3 计算 PI 的 N 位数 python 切长数

Question

i need to write a script that get input from client of an number and i need to print back the PI number until client number for example: client number is 52 --> 3.14159265358979323846264338327950288419716939937510

so far i write this:

sum = 0

for i in range(1, 1001):
    sum += ((-1)**(i+1))*4 / ((i + i)*(i + i + 1)*(i + i + 2))

print(sum)

the issue is that python showing to me only the 17 decimals digits, and i expect to see the 1000 decimal digits. there is a way to showing all the decimal digits based on the inputed range? it's for school task, so i need to write is as simple as it can be.

Answer 1

I do not think it is possible to get aa float value with a 1000point precision.

Check https://stackoverflow.com/a/54967370/11152011 to calculate pi up to n-precision

You can then use the "decimal" library to use the string as a number.

The calculation of pi was taken from the above link.

import decimal

DIGITS = 1000

def pi_digits(x):
    k,a,b,a1,b1 = 2,4,1,12,4
    while x > 0:
        p,q,k = k * k, 2 * k + 1, k + 1
        a,b,a1,b1 = a1, b1, p*a + q*a1, p*b + q*b1
        d,d1 = a/b, a1/b1
        while d == d1 and x > 0:
            yield int(d)
            x -= 1
            a,a1 = 10*(a % b), 10*(a1 % b1)
            d,d1 = a/b, a1/b1

digits = [str(n) for n in list(pi_digits(DIGITS))]
str_pi='{}.{}'.format(digits.pop(0), "".join(digits)

context = decimal.Context(prec=100)
decimal.setcontext(context)
pi = decimal.Decimal(str_pi)
print(pi+5)
print(pi*20)

Answer 2

I don't know how accurate is this but for a small class assignment i guess do the following:

num=52 #input
pi=22/7;
print('{:.{}f}'.format(pi, num))