Game of Life

gameoflife.py

import pygame as pg
import sys
import collections

# Number of cells
CELL_GRID_WIDTH = 50
CELL_GRID_HEIGHT = 50

# Visible size of the cell
CELL_WIDTH = 10
CELL_HEIGHT = 10

pg.init()
screen = pg.display.set_mode((CELL_GRID_WIDTH * CELL_WIDTH, CELL_GRID_HEIGHT * CELL_HEIGHT))

CELL_SURF = pg.Surface((CELL_WIDTH, CELL_HEIGHT))
CELL_SURF.fill((255, 255, 255), ((0,0), (9, 9)))

GLIDER = [
    " X",
    "  X",
    "XXX",
]


def load_initial(cells, pos, initial):
    x, y = pos
    for y_offset, row in enumerate(initial):
        for x_offset, marker in enumerate(row):
            if marker != " ":
                cells[x + x_offset, y + y_offset] = 1


def evolve(cells):
    """Evolves cells according to rules"""
    # Note: Grid is "infinite"

    new_cells = collections.defaultdict(lambda: 0)

    for x in range(CELL_GRID_WIDTH):
        for y in range(CELL_GRID_HEIGHT):
            # Calculate number of neighbours
            new_cells[x, y] += cells[x - 1, y]  # left
            new_cells[x, y] += cells[x + 1, y]  # right
            new_cells[x, y] += cells[x, y - 1]  # top
            new_cells[x, y] += cells[x, y + 1]  # bottom
            new_cells[x, y] += cells[x - 1, y - 1]  # topleft
            new_cells[x, y] += cells[x + 1, y + 1]  # bottomright
            new_cells[x, y] += cells[x + 1, y - 1]  # topright
            new_cells[x, y] += cells[x - 1, y + 1]  # bottomleft

            if new_cells[x, y] == 2 and cells[x, y]:
                new_cells[x, y] = 1
            elif new_cells[x, y] == 3:
                new_cells[x, y] = 1
            else:
                new_cells[x, y] = 0

    return new_cells


def draw_cells(cells, screen):
    rect = pg.Rect((0, 0), (CELL_WIDTH, CELL_HEIGHT))

    for x in range(CELL_GRID_WIDTH):
        for y in range(CELL_GRID_HEIGHT):
            if cells[x, y]:
                rect.x = x * CELL_WIDTH
                rect.y = y * CELL_HEIGHT
                screen.blit(CELL_SURF, rect)


def life(cells):
    clock = pg.time.Clock()
    evolve_timer = 500

    # Main game loop
    while True:
        dt = clock.tick(30)

        for event in pg.event.get():
            if event.type == pg.QUIT:
                sys.exit()

        evolve_timer -= dt
        if evolve_timer <= 0:
            # Evolve cells
            evolve_timer = 1000
            cells = evolve(cells)

        screen.fill((0, 0, 0))

        # Draw current state
        draw_cells(cells, screen)

        pg.display.flip()

if __name__ == "__main__":
    cells = collections.defaultdict(lambda: 0)
    load_initial(cells, (20, 20), GLIDER)
    life(cells)