How to take numbers from a .txt list and save the result in another .txt?

Question

This script has a formula where at the beginning the numbers x1 and x2 in the code are set, and I need to change the code so that the value x1 is taken from the list pre-prepared text document For example, from a document: 'List.txt'

That is, it turns out I need to enter:

with open ("List.txt '", "r") as f:

into place the value x1 = 6 in the code. But how to systematize it? Just not very rich in knowledge of Python.

List of numbers:

1
4
2
15
6
8
13
3
12
5
10
7
14
9
11

Code: (Powered by Python 2.7)

import sys

a=0
b=7
p=37

x1=6
x2=8

if (len(sys.argv)>1):
    x1=int(sys.argv[1])
if (len(sys.argv)>2):
    x2=int(sys.argv[2])
if (len(sys.argv)>3):
    p=int(sys.argv[3])
if (len(sys.argv)>4):
    a=int(sys.argv[4])
if (len(sys.argv)>5):
    b=int(sys.argv[5])


def modular_sqrt(a, p):
    """ Find a quadratic residue (mod p) of 'a'. p
        must be an odd prime.

        Solve the congruence of the form:
            x^2 = a (mod p)
        And returns x. Note that p - x is also a root.

        0 is returned is no square root exists for
        these a and p.

        The Tonelli-Shanks algorithm is used (except
        for some simple cases in which the solution
        is known from an identity). This algorithm
        runs in polynomial time (unless the
        generalized Riemann hypothesis is false).
    """
    # Simple cases
    #

    if legendre_symbol(a, p) != 1:
        return 0
    elif a == 0:
        return 0
    elif p == 2:
        return p
    elif p % 4 == 3:
        return pow(a, (p + 1) / 4, p)

    # Partition p-1 to s * 2^e for an odd s (i.e.
    # reduce all the powers of 2 from p-1)
    #
    s = p - 1
    e = 0
    while s % 2 == 0:
        s /= 2
        e += 1

    # Find some 'n' with a legendre symbol n|p = -1.
    # Shouldn't take long.
    #
    n = 2
    while legendre_symbol(n, p) != -1:
        n += 1

    x = pow(a, (s + 1) / 2, p)
    b = pow(a, s, p)
    g = pow(n, s, p)
    r = e

    while True:
        t = b
        m = 0
        for m in xrange(r):
            if t == 1:
                break
            t = pow(t, 2, p)

        if m == 0:
            return x

        gs = pow(g, 2 ** (r - m - 1), p)
        g = (gs * gs) % p
        x = (x * gs) % p
        b = (b * g) % p
        r = m


def legendre_symbol(a, p):
    """ Compute the Legendre symbol a|p using
        Euler's criterion. p is a prime, a is
        relatively prime to p (if p divides
        a, then a|p = 0)


        Returns 1 if a has a square root modulo
        p, -1 otherwise.
    """
    ls = pow(a, (p - 1) / 2, p)
    return -1 if ls == p - 1 else ls

def egcd(a, b):
    if a == 0:
        return (b, 0, 1)
    else:
        g, y, x = egcd(b % a, a)
        return (g, x - (b // a) * y, y)

def modinv(a, m):
    g, x, y = egcd(a, m)
    if g != 1:
        print ("x")
    else: 
       return x % m


print "a=",a
print "b=",b
print "p=",p

print "x-point=",x1
print "x-point=",x2


z=(x1**3 + a*x1 +b) % p
y1=modular_sqrt(z, p)

z=(x2**3 + a*x2 +b) % p
y2=modular_sqrt(z, p)

print "\nP1\t(%d,%d)" % (x1,y1)
print "P2\t(%d,%d)" % (x2,y2)



s=((-y2)-y1)* modinv(x2-x1,p) 

x3=(s**2-x2-x1) % p

y3=((s*(x2-x3)+y2)) % p

result =  "Q\t(%d,%d)" % (x3,y3)
f = open('Result01.txt', 'w')
f.write(result)
f.close()

Earlier, I saw scripts where numbers are taken from one text document, perform a function, and the result is saved in another text document.

Answer 1

Try using the pandas library to read, process and write your numbers.

import pandas as pd    # import pandas module and call it pd for short
x2 = 6                 
df = pd.read_csv('input_file.txt')    # read the data from a text file into a dataframe
df['x1 times x2'] = df['x1'] * x2     # create new column in your dataframe with result of your function
df.to_csv('output_file.txt', index=False)    # output result of your calculations (dropping the dataframe index column)

Answer 2

Although you're hard coding the values of x1, x2, in your code, they can be redefined, as you're doing here:

if (len(sys.argv)>1):
    x1=int(sys.argv[1])
if (len(sys.argv)>2):
    x2=int(sys.argv[2])

So if you call your script from command line, like C:\Users\test.py x1value x2value you can redefine x1 and x2. If you really want a text file to contain your x1 and x2, just use the following snippet somewhere at the top

import json
with open("input.json","r",encoding="utf-8") as stream:
    parsed = json.load(stream)
    x1,x2 = parsed["x1"],parsed["x2"]

Contents of "input.json":

{"x1":1,"x2"=2}

Answer 3

With only python without extra dependencies, your can read List.txt as follow

with open("List.txt","r") as f:
    arrX1 = list(map(int,f.readlines()))

print (arrX1)

The above reads all the lines in f and converts/maps them to integers. The list function then gives you an array you can loop through to generate x2 and write to the Result.txt file.

The above prints

[1, 4, 2, 15, 6, 8, 13, 5, 3, 10, 7, 14, 9, 11]

So for your code replace all lines from 125 downward with

# Read numbers from file and put them in an array
with open("List.txt","r") as f:
    arrX1 = list(map(int,f.readlines()))
f.close()

# Open the result file to write to
f = open('Result01.txt', 'w')

# Now get x1 for each item in the list of numbers from the file
# then do the calculations
# and write the result
for x1 in arrX1:
    z=(x1**3 + a*x1 +b) % p
    y1=modular_sqrt(z, p)

    z=(x2**3 + a*x2 +b) % p
    y2=modular_sqrt(z, p)

    print "\nP1\t(%d,%d)" % (x1,y1)
    print "P2\t(%d,%d)" % (x2,y2)

    s=((-y2)-y1)* modinv(x2-x1,p) 

    x3=(s**2-x2-x1) % p

    y3=((s*(x2-x3)+y2)) % p

    result =  "Q\t(%d,%d)" % (x3,y3)
    f.write(result)

f.close()