Queens solution in python

#!/usr/bin/env python2.5

import random

def conflict(state, nextX): 

    nextY = len(state) 

    for i in range(nextY): 

        if abs(state[i]-nextX) in (0, nextY-i): 

            return True 

    return False

def queens(num , state=()):

for pos in range(num):

if not conflict(state, pos):

if len(state) == num - 1:

yield (pos,)

else:

for result in queens(num, state + (pos,)):

yield (pos,) + result

def prettyprint(solution):

def line(pos, length=len(solution)):

return '. '*(pos) + 'X ' + '. '* (length - pos - 1)

for pos in solution:

print line(pos)

prettyprint(random.choice(list(queens(8))))