At 26/12/2003 11:45, you wrote: After you correct your indentation error, there is another issue: > def __str__(self): > print '(' + str(self.x) + str(self.y) + ')' This should *return* a string, not print it. Try: return '(%s,%s)' % (self.x, self.y) Gabriel Genellina Softlab SRL