This python script finds the multiplicative inverse of X mod Y

Extended_Euclidean_algm.py

from sys import stdout

rs = []
qs = [' ',' ']
xs = [1,0]
ys = [0,1]

def gcd(a, b):
    if(len(rs) is 0):
        rs.append(a)
    if(b > 0):
        rs.append(b)
        r = a % b
        q = int((a - r) / b)
        qs.append(q)
        x = xs[-2] - xs[-1] * q
        xs.append(x)
        y = ys[-2] - ys[-1] * q
        ys.append(y)
        gcd(b, r)
        
def print_it():
    for x in range(len(rs)):
        stdout.write(str(rs[x]) + "\t" + str(qs[x]) + "\t" + str(xs[x]) + "\t" + str(ys[x]) + "\n")
    temp = rs[0] * xs[-2] + rs[1] * ys[-2]
    stdout.write("\n")
    stdout.write(str(rs[0]) + " * " + str(xs[-2]) + " + " + str(rs[1]) + " * " + str(ys[-2]) + " = " + str(temp))
    stdout.write("\n")
    if(1 is (rs[1] * ys[-2]) % rs[0]):
        stdout.write('1 ≣ (' + str(rs[1]) + " * " + str(ys[-2]) + ') mod ' + str(rs[0]))
        stdout.write("\nmultiplicative inverse of " + str(rs[1]) + " is " + str(ys[-2]))
    else:
        print("error")
    stdout.write("\n")
    
def reset():
    rs[:] = []
    qs[:] = [' ',' ']
    xs[:] = [1,0]
    ys[:] = [0,1]
    print("="*30)
    
gcd(4321, 2410)
print_it()
reset()
gcd(1769, 550)
print_it()