small python script to generate a wolfram cellular automaton

wolfram.py

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

'''
Created on 29 Apr 2014

@author: Steven Kay

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
'''

ch = u"▓"
blank = " "
sett = {0:blank, 1:ch}

def getrules(ruleno):
    rules={}
    for x in range(0, 8):
        rules[x] = (ruleno >> x) & 0x1
    return rules
        
def getgen(rules, input):
    op = []
    wid = len(input)
    for ix in range(0, wid):
        left = (ix - 1) % wid
        right = (ix + 1) % wid
        value = ((input[left] == ch) << 2) | ((input[ix] == ch) << 1) | ((input[right] == ch))
        op.append(sett[rules[value]])
    return op

def getstartconfig(wid):
    half = ((wid / 2) - 2)
    return ((blank * half) + ch + (blank * half))

def loop(ruleno, wid):
    op = getstartconfig(wid)
    rules = getrules(ruleno)
    s = "".join(op)
    while True:
        print s
        op = getgen(rules, op)
        s = "".join(op)

# loop(rule_number, width_in_characters)        
loop(30, 132)