highprecision_squareroot.py

# high precision square root
# Newton's method
# Juhani Kaukoranta 11.11.2018

import math
from decimal import *
def Newton(x,precision) :
    '''high precision square root'''
    if x > 0 :
        getcontext().prec=precision
        x0 = Decimal(1)
        for n in range (0,70):
            x1 = (x0 + Decimal(x)/x0)/Decimal(2)
            x0 = x1
        return(x0)
    if x == 0 :
        return(0)

    if x < 0 :
        print("Only non-negative number has a square root")
a = input("Give non-negative number from which to get square root ")
x = float(a)
if x >= 0 :
    precision = int(input("How many digits precision, f.eq 100 "))
    print("sqrt(",a,") = ",Newton(x,precision))
else:
    print("Only non-negative number has square root")