matrix.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import random
import math

def zeroify(matrix):
    height = len(matrix)
    width = len(matrix[0])
    p = primes(width + height)
    a = 1
    for row in range(0, height):
        for col in range(0, width):
            if matrix[row][col] == 0:
                a *= p[col] * p[width + row]
    for row in range(0, height):
        for col in range(0, width):
            if a % p[col] == 0 or a % p[width + row] == 0:
                matrix[row][col] = 0
    return matrix

def main():
    mat = randomMatrix(random.randint(3,10), random.randint(3,10))
    for i in range(0, 3):
        mat[random.randint(0, len(mat) - 1)][random.randint(0, len(mat[0]) - 1)] = 0
    print "Initial matrix:"
    print prettify(mat)
    print "Zeroed matrix:"
    print prettify(zeroify(mat))


## UTILITY FUNCTIONS ##

def primes(n):
    """ Returns a list of n primes """
    return sieve(int(math.ceil(n*math.log(n*math.log(n)))))[0:n]

def sieve(n):
    """ Returns  a list of primes < n """
    sieve = [True] * (n/2)
    for i in xrange(3,int(n**0.5)+1,2):
        if sieve[i/2]:
            sieve[i*i/2::i] = [False] * ((n-i*i-1)/(2*i)+1)
    return [2] + [2*i+1 for i in xrange(1,n/2) if sieve[i]]

def randomMatrix(width, height):
    matrix = []
    for i in range(0, height):
        row = []
        for j in range(0, width):
            row += [random.randint(0,255)]
        matrix += [row]
    return matrix

def prettify(matrix):
    ret = u"┌ " + (" " * len(matrix[0]) * 4) + u"┐\n"
    for row in matrix:
        rowstr = u"│ "
        for elem in row:
            elemstr = str(elem)
            rowstr += elemstr + (" " * (4 - len(elemstr)))
        rowstr += u"│\n"
        ret += rowstr
    ret += u"└ " + (" " * len(matrix[0]) * 4) + u"┘"
    return ret

if __name__ == "__main__":
    main()