Cellular Automata Example

class Automata():
    'Represents a cellular automata with configurable params:'
    ' - number of columns, defaults to 64'
    ' - number of iterations, defaults to 32'
    ' - true symbol, defaults to *'
    ' - false symbol, defaults to -'
    entries = []
    rows = 0
    cur_row = 0

    def __init__(self, cols=64, iters=32, t_symbol="*", f_symbol="-"):
        print "Beginning Cellular Automata Simulation"
        print "Press CTRL+C to quit."
        self.cols = cols
        self.iterations = iters
        self.true_symbol = t_symbol
        self.false_symbol = f_symbol
        try:
            while self.cur_row < self.iterations:
                self.add_row()
                self.print_row()
                self.cur_row += 1
        except KeyboardInterrupt:
            print "Exiting."
            return False

    def set_first_row_position(self):
        self.first_row_position = (self.cols / 2) - 1
        return self.first_row_position

    def get_previous_row_column(self, col):
        if self.cur_row > 0:
            previous_row = self.entries[self.cur_row - 1]
            return previous_row[col]
        else:
            return False

    def print_row(self):
        return_val = ""
        for i in range(0, self.cols - 1):
            col = self.entries[self.cur_row][i]
            if col == True:
                return_val += self.true_symbol
            elif col == False:
                return_val += self.false_symbol
            else:
                return_val += self.false_symbol
        print return_val
        return return_val

    def add_row(self):
        self.entries.append([])
        self.entries[self.cur_row] = [False] * self.cols
        if self.cur_row == 0:
            automata_start = self.set_first_row_position()
            self.entries[self.cur_row][automata_start] = True
        else:
            for i in range(self.cols):
                pos_left = i - 1
                pos_right = i + 1
                if (pos_left > 0):
                    prev_pos_left = self.get_previous_row_column(pos_left)
                else:
                    prev_pos_left = False
                if (pos_right < self.cols):
                    prev_pos_right = self.get_previous_row_column(pos_right)
                else:
                    prev_pos_right = False
                if prev_pos_right == True and prev_pos_left == False:
                    return_val = True
                elif prev_pos_left == True and prev_pos_right == False:
                    return_val = True
                else:
                    return_val = False
                self.entries[self.cur_row][i] = return_val
        return self.entries[self.cur_row]

Automata()