Sierpinski's carpet

#!/usr/bin/python
# -*- coding: utf-8 -*-
import numpy as np
from matplotlib import pyplot as plt

n = 5
m = 3**n
carpet = np.ones((m, m), dtype=bool) # create two-dimensional bitarray

def sierpinski(a, b, l, n): # a,b - offset; l - length
    if n == 0:
        return
    l /= 3 # offset of centre
    for x in xrange(l+a, l+l+a):
        for y in xrange(l+b, l+l+b):
            carpet[x][y] = False
    sierpinski(a+0,   b+0,   l, n-1)
    sierpinski(a+0,   b+l,   l, n-1)
    sierpinski(a+0,   b+l+l, l, n-1)

    sierpinski(a+l,   b+0,   l, n-1)
    sierpinski(a+l,   b+l+l, l, n-1)

    sierpinski(a+l+l, b+0,   l, n-1)
    sierpinski(a+l+l, b+l,   l, n-1)
    sierpinski(a+l+l, b+l+l, l, n-1)


sierpinski(0, 0, m, n)

plt.imshow(carpet, interpolation='nearest')
""" hide axes and show the sierpinski's carpet """
plt.gca().axes.get_xaxis().set_visible(False)
plt.gca().axes.get_yaxis().set_visible(False)
plt.show()