#!/usr/bin/env python

# A flexible 2D Cellular Automata computation and display engine in Python.

# Copyright 2013 by Akkana Peck.

# Share and enjoy under the terms of the GPL v2 or later.

import sys

import time

import random

import gtk, gobject

class Cellgrid:

def __init__(self, nrows, ncols):

self.nrows = nrows

self.ncols = ncols

self.grid = [[0] * ncols for i in xrange(nrows)]

self.iterations = 0

# characters is used in __repr__ for printing the grid

self.characters = None

def randomize(self, probabilities):

'''Initialize the grid to random values specified by the probailities

argument. probabilities should be a tuple or list of floating

point values adding to 1. The number of entries in probabilities

controls what integer values the grid can take.

'''

for r in range(self.nrows):

for c in range(self.ncols):

tot = 0

for i, prob in enumerate(probabilities):

tot += prob

if random.random() <= tot:

self.grid[r][c] = i

break # break out of the inner loop over probabilities

def item(self, coords):

'''Return the item at the given coordinates,

accounting for periodic boundary conditions.

'''

return self.grid[coords[0] % self.nrows][coords[1] % self.ncols]

def setitem(self, coords, val):

'''Set the given item to the given value.

'''

self.grid[coords[0] % self.nrows][coords[1] % self.ncols] = val

def update(self, rule):

'''Update self.grid using the given rule.

Replaces self.grid with the new grid.

rule should have the signature

rule(cellgrid, (row, col)) -> int

'''

self.newgrid = []

for r in xrange(self.nrows):

self.newgrid.append([])

for c in xrange(self.ncols):

self.newgrid[r].append(rule(self, (r, c)))

self.grid = self.newgrid

self.iterations += 1

def quit(self):

print self.iterations, "iterations"

sys.exit(0)

def run_plot(self, stepsecs=.1):

'''Iterate over the rule, plotting the evolving grid

'''

def __repr__(self):

out = ''

for row in self.grid:

for cell in row:

if self.characters:

out += self.characters[cell]

else:

out += '%3d' % cell

out += '\n'

return out

class CAWindow:

def __init__(self, cellgrid, rule=None, timeout = 1):

'''Timeout in milliseconds

'''

self.cellgrid = cellgrid

self.rule = rule

self.drawing_area = None

self.fgc = None

self.bgc = None

self.width = 0

self.height = 0

self.running = False

self.timeout = timeout

def draw(self):

'''Draw the current state of the cell grid

'''

# Clear the background:

self.drawing_area.window.draw_rectangle(self.bgc, True, 0, 0,

self.width, self.height)

# What's the size of each cell?

w = self.width / self.cellgrid.ncols

h = self.height / self.cellgrid.nrows

# Draw the cells

for r in xrange(self.cellgrid.ncols):

for c in xrange(self.cellgrid.nrows):

if cellgrid.item((r, c)):

self.fgc.set_rgb_fg_color(gtk.gdk.Color(65535, 0, 65535))

else:

self.fgc.set_rgb_fg_color(gtk.gdk.Color(512, 512, 512))

self.drawing_area.window.draw_rectangle(self.fgc, True,

c * w, r * h,

w, h)

def idle_handler(self, widget):

self.cellgrid.update(self.rule)

self.draw()

# Return True so we'll be called again:

if self.running:

return True

def key_press_event(self, widget, event) :

if event.string == "q" :

self.cellgrid.quit()

return True

if event.string == " " :

self.cellgrid.update(self.rule)

self.draw()

self.running = False

return True

if event.string == "c" :

if self.running:

return True

self.running = True

gobject.timeout_add(self.timeout, self.idle_handler,

self.drawing_area)

return True

return False

def expose_handler(self, widget, event):

# print "Expose"

if not self.fgc:

self.fgc = widget.window.new_gc()

self.bgc = widget.window.new_gc()

self.bgc.set_rgb_fg_color(gtk.gdk.Color(0, 0, 0))

self.width, self.height = self.drawing_area.window.get_size()

self.draw()

return True

def start(self):

win = gtk.Window()

win.connect("key-press-event", self.key_press_event)

self.drawing_area = gtk.DrawingArea()

self.drawing_area.connect("expose-event", self.expose_handler)

win.add(self.drawing_area)

self.drawing_area.show()

win.connect("destroy", gtk.main_quit)

win.set_default_size(512, 512)

win.show()

gtk.main()

def life(cellgrid, cawin):

'''Initialize the grids to play Conway's Game of Life.

'''

def liferule(cellgrid, coords):

# Count the total number of neighbors, not including the cell itself:

tot = 0

for i in (-1, 0, 1):

for j in (-1, 0, 1):

if i == 0 and j == 0:

continue

tot += cellgrid.item((coords[0]+i, coords[1]+j))

# With 3 neighbors, there will always be a cell there:

if tot == 3:

return 1

# 2 neighbors lets an existing cell live on:

if tot == 2 and cellgrid.item(coords):

return 1

# Otherwise it dies, of lonliness or overcrowding:

return 0

# Initialize with a glider:

cellgrid.setitem((0, 2), 1)

cellgrid.setitem((1, 2), 1)

cellgrid.setitem((2, 2), 1)

cellgrid.setitem((2, 1), 1)

cellgrid.setitem((1, 0), 1)

cellgrid.randomize((.5, .5))

cawin.rule = liferule

def neighbor(cellgrid, cawin):

'''Initialize the grid to simulate Thomas Schelling's

segregated neighborhood study.

'''

def neighbor_rule(cellgrid, coords):

x, y = coords

tot = cellgrid.item((x-1, y)) + cellgrid.item((x+1, y)) \

+ cellgrid.item((x, y-1)) + cellgrid.item((x, y+1))

# Total of 4 neightbors. If less than 2 are the same color as x, y

# then the resident is unhappy, and sells out to someone of the

# other color.

cur = cellgrid.item(coords)

if tot >= 2:

return cur

else:

return int(not cur)

# Initialize with 50% probability:

cellgrid.randomize((.5, .5))

cawin.rule = neighbor_rule

if __name__ == "__main__":

# Some sample rules:

# Set up the grid:

cellgrid = Cellgrid(50, 50)

cawin = CAWindow(cellgrid)

life(cellgrid, cawin)

#neighbor(cellgrid, cawin)

cawin.start()

# Show characters, not numbers:

#cellgrid.characters = '.*'

#cellgrid.characters = [' .', ' *' ]

#

# print "Shouldn't ever get here"

# while True:

# print ""

# print "====================="

# print cellgrid

# cellgrid.update(life)

# time.sleep(.1)