cellaut.py

#!/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)