A simple little module to complete the prime number challenge. Includes 4 tests. This could be made to be much much faster if we used PyPy and NumPy, but the challenge was to utilize the standard library only. To run the tests, run: `python -m unittest prime-challenge`

prime-challenge.py

#!/usr/bin/env python

import itertools
import unittest


def primeGenerator():
    """
    Yields an array of primes.
    """
    primes = [2]
    sequence = 0
    yield primes
    for candidate in itertools.count(3, 2):
        prime = True

        for sequence in primes:
            # mod check
            if candidate % sequence == 0:
                prime = False
                break

            # exp check
            if sequence ** 2 > candidate:
                break

        if prime:
            primes.append(candidate)
            yield primes


def primeMatrix(num_primes):
    """
    Generates a two dimensional array of prime products.
    """
    gen = primeGenerator()
    for _ in range(1, num_primes):
        next(gen)

    primes = next(gen)
    prime_grid = [[0] + primes]

    for x_idx, x_value in enumerate(primes):
        prime_grid.append([x_value])

        for y_idx, y_value in enumerate(primes):
            prime_grid[-1].append(x_value * y_value)

    return prime_grid


def formatMatrix(matrix):
    """
    Returns a nicely formatted string of the two dimensional matrix
    """
    return '\n'.join([
        ''.join(['{:4}'.format(item) for item in row]) for row in matrix
        ])


class TestPrimeTools(unittest.TestCase):

    def setUp(self):
        self.matrix = primeMatrix(10)
        self.first_10_primes = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29]

    def testPrimeGenerator(self):
        gen = primeGenerator()
        primes = []
        for _ in range(0, 10):
            primes = next(gen)

        self.assertEqual(
                primes,
                self.first_10_primes,
                'The first 10 primes are incorrect.'
                )

    def testFirstRow(self):
        self.assertEqual(
                self.matrix[0][1:],
                self.first_10_primes,
                'The first row is incorrect.'
                )

    def testFirstColumn(self):
        self.assertEqual(
                [row[0] for row in self.matrix[1:]],
                self.first_10_primes,
                'The first column is incorrect.'
                )

    def testMatrix(self):
        expected_matrix = [
                [0,  2,  3,  5,  7, 11, 13, 17, 19, 23, 29],
                [2,  4,  6, 10, 14, 22, 26, 34, 38, 46, 58],
                [3,  6,  9, 15, 21, 33, 39, 51, 57, 69, 87],
                [5, 10, 15, 25, 35, 55, 65, 85, 95, 115, 145],
                [7, 14, 21, 35, 49, 77, 91, 119, 133, 161, 203],
                [11, 22, 33, 55, 77, 121, 143, 187, 209, 253, 319],
                [13, 26, 39, 65, 91, 143, 169, 221, 247, 299, 377],
                [17, 34, 51, 85, 119, 187, 221, 289, 323, 391, 493],
                [19, 38, 57, 95, 133, 209, 247, 323, 361, 437, 551],
                [23, 46, 69, 115, 161, 253, 299, 391, 437, 529, 667],
                [29, 58, 87, 145, 203, 319, 377, 493, 551, 667, 841]]

        self.assertEqual(
                self.matrix,
                expected_matrix,
                'The matrix format is incorrect.'
                )


if __name__ == "__main__":
    print(formatMatrix(primeMatrix(10)))

Here's the execution profile under PyPy. Notice the MUCH faster execution time, and slightly less memory usage than the standard variant above, but still more memory usage than the NumPy variant, and it's slower.