Multiplication algorithms (version 1.0)

#! python3
# -*- encoding: utf-8 -*-

#https://www.coursera.org/learn/algorithms-divide-conquer
#Lab 1, Ulf Benjaminsson, 2016-12-14
import sys;
NUMBER_A = 3141592653589793238462643383279502884197169399375105820974944592;
NUMBER_B = 2718281828459045235360287471352662497757247093699959574966967627;

#(a, b, product)
def makeTestCase(a, b):
    return (a, b, a*b);

def makeTestCases():
    return [
        makeTestCase(1, 1),
        makeTestCase(11, 10),
        makeTestCase(-100, 200),
        makeTestCase(314159, 271828),
        makeTestCase(10, 100),
        makeTestCase(-10, 100),
        makeTestCase(NUMBER_A, NUMBER_B)
    ];

#implements https://en.wikipedia.org/wiki/Grid_method_multiplication
#As a warmup to more proper algorithms.
def gridAlgo(a,b):
    negate = not ((a < 0) == (b < 0)); #compare sign of the numbers (mixed sign multiplication = negative result)
    digits_a = [int(i) for i in str(abs(a))];
    digits_b = [int(i) for i in str(abs(b))];
    digits_a.reverse(); #arrange digits in order of magnitude; 1s, 10s, 100s etc
    digits_b.reverse(); #to keep my loops simple. :)
    factors = [[0] * len(digits_b) for i in range(len(digits_a))]; #2 dimensional array of [digits_a x digits_b] indexes
    for pos_a, digit_a in enumerate(digits_a):
        digit_a_value = digit_a * (10**pos_a); #10**pos_a == 10^n == place value in base 10
        for pos_b, digit_b in enumerate(digits_b):
            digit_b_value = digit_b * (10**pos_b); #10**pos_b == 10^n == place value in base 10
            factors[pos_a][pos_b] = digit_a_value * digit_b_value;
    return -sum(sum(factors,[])) if negate else sum(sum(factors,[]));

#TODO:
def gradeSchoolAlgo(a,b):
    result = 0;
    return result;

#TODO:
def karatsubaAlgo(a,b):
    result = 0;
    return result;

def multiply(a, b):
    result = gridAlgo(a,b);
    return result;

def main():
    samples = makeTestCases();
    for (a, b, correctAnswer) in samples:
        result = multiply(a, b);
        passed = result ==  correctAnswer;
        print('{!s} {:d} x {:d} = {:d}'.format(
                "Passed:" if passed else "\tFailed:", a, b, result)
        );
        if(not passed):
           print('\tShould be: {:d}'.format(correctAnswer)) ;
    return 0;

if __name__ == '__main__':
    status = main();
    sys.exit(status);