Wsrtjtyk

I am currently trying to program a python 3 implementation of the game of life. My main goal was to display a grid of the size n that gets filled randomly according to conway's rules.
That part works fine.

Now I wanted to implement a second mode that allows you to start with one of the given formations - in my first try a glider.

Here is the main():

import matplotlib.pyplot as plt

import matplotlib.animation as animation

from gol_functions import *



def main():



    # get arguments from input function

    arguments = input_arguments()

    # set the arguments 

    gridsize = int(arguments.gridsize)

    interval = int(arguments.interval)

    formation = arguments.formationflag



    # if you want to start with a formation:

    if formation:

        grid = np.zeros(gridsize*gridsize).reshape(gridsize, gridsize)

        add_glider(1, 1, grid)



    # else display a randopm grid

    else:

        grid = randomgrid(gridsize)



    fig, ax = plt.subplots()



    # colormap: black -> alive, white -> dead

    img = ax.imshow(grid, cmap='binary', interpolation='nearest')



    # this will be used to save the animation in a later version

    ani = animation.FuncAnimation(fig, update, fargs=(img, grid, gridsize,),

                                  frames=10,

                                  interval=interval,

                                  save_count=50)



    # remove x and y - axis labels, numbers and ticks

    ax.axes.xaxis.set_ticklabels()

    ax.axes.yaxis.set_ticklabels()

    plt.xticks()

    plt.yticks()



    # plot the animated output

    plt.show()





    if __name__ == '__main__':

        main()

Here is the function for adding the glider:

def add_glider(i, j, grid):

    """adds a glider with top-left cell at (i, j)"""

    glider = np.array([[0,    0, 255],

                       [255,  0, 255],

                       [0,  255, 255]])



    grid[i:i+3, j:j+3] = glider

It adds a glider in the grid @ position 1, 1

And here is my update function:

def update(frameNum, img, grid, gridsize):

    """Updates the grid every time it is refreshed"""

    newgrid = grid.copy()

    for i in range(gridsize):

        for j in range(gridsize):

            # this formula considers the edge/boundary conditions that appear

            # every cell has to have 8 neighbouring cells

            # to implement this in a grid of size n we simply fold the 4 edges to each parallel edge

            # we'll end up with a cylinder first, then with a geometric shape called torus (google it.)

            total = int((grid[i, (j - 1) % gridsize] + grid[i, (j + 1) % gridsize] +

                         grid[(i - 1) % gridsize, j] + grid[(i + 1) % gridsize, j] +

                         grid[(i - 1) % gridsize, (j - 1) % gridsize] +             

                         grid[(i - 1) % gridsize, (j + 1) % gridsize] +

                         grid[(i + 1) % gridsize, (j - 1) % gridsize] + grid[

                         (i + 1) % gridsize, (j + 1) % gridsize]) / 255)



        # apply conway's basic rules of the game of life for each cell

            if grid[i, j] == ON:

                if (total < 2) or (total > 3):

                    newgrid[i, j] = OFF

            else:

                if total == 3:

                    newgrid[i, j] = ON

                    # update data

                    img.set_data(newgrid)

                    grid[:] = newgrid[:]

                    return img,

However when I run it with the option to have it display the glider, all I see is the following formation...

failedglider_1.png

which swiftly turns into this and becomes static:

failedglider_2.png

... instead of an actual glider as seen in the matrix of add_glider. So it seems that somehow the program adds an unwanted alive cell right at the top. I tried to find where it comes from... but I can't find it.

Does anyone have any clues? I am greatful for all help.
Thanks in advance!

With some minor fixes to the code from your original post I am able to produce exactly what you wanted. The modified code is listed at the bottom. First frame is shown on the left in the image bellow. After few frames it looks like the image on the right.
So the glider seems to work just fine :)

#!/usr/bin/python

# call with: python3 cgl.py 10 500 1 1



import os

import argparse

import numpy as np

import matplotlib.pyplot as plt

from matplotlib import animation



ON = 255

OFF = 0





def update(frameNum, img, grid, gridsize):

    """Updates the grid every time it is refreshed"""

    newgrid = grid.copy()

    for i in range(gridsize):

        for j in range(gridsize):

            # this formula considers the edge/boundary conditions that appear

            # every cell has to have 8 neighbouring cells

            # to implement this in a grid of size n we simply fold the 4 edges to each parallel edge

            # we'll end up with a cylinder first, then with a geometric shape called torus (google it.)

            total = int((grid[i, (j - 1) % gridsize] + grid[i, (j + 1) % gridsize] +

                         grid[(i - 1) % gridsize, j] + grid[(i + 1) % gridsize, j] +

                         grid[(i - 1) % gridsize, (j - 1) % gridsize] +

                         grid[(i - 1) % gridsize, (j + 1) % gridsize] +

                         grid[(i + 1) % gridsize, (j - 1) % gridsize] + grid[

                         (i + 1) % gridsize, (j + 1) % gridsize]) / 255)



        # apply conway's basic rules of the game of life for each cell

            if grid[i, j] == ON:

                if (total < 2) or (total > 3):

                    newgrid[i, j] = OFF

            else:

                if total == 3:

                    newgrid[i, j] = ON

    # update data

    grid[:] = newgrid[:]

    img.set_data(newgrid)

    return img,





def add_glider(i, j, grid):

    """adds a glider with top-left cell at (i, j)"""

    glider = np.array([[0,    0, 255],

                       [255,  0, 255],

                       [0,  255, 255]])



    grid[i:i+3, j:j+3] = glider





def main():

    parser = argparse.ArgumentParser(description="Conway's game of life in Python 3")

    parser.add_argument('gridsize', type=int, help='Dimension of grid.')

    parser.add_argument('interval', type=int, help='Interval.')

    parser.add_argument('formationflag', type=bool, help='Predefined formation.')

    parser.add_argument('frame', type=int, help='How many frames to animate.')



    # get arguments from input function

    arguments = parser.parse_args()

    # set the arguments

    frame = int(arguments.frame)

    gridsize = int(arguments.gridsize)

    interval = int(arguments.interval)

    formation = arguments.formationflag



    # if you want to start with a formation:

    if formation:

        grid = np.zeros(gridsize*gridsize).reshape(gridsize, gridsize)

        add_glider(1, 1, grid)



    # else display a randopm grid

    else:

        grid = randomgrid(gridsize)



    fig, ax = plt.subplots()



    # colormap: black -> alive, white -> dead

    img = ax.imshow(grid, cmap='binary', interpolation='nearest')



    # # this will be used to save the animation in a later version

    ani = animation.FuncAnimation(fig, update, fargs=(img, grid, gridsize,),

                                  frames=frame,

                                  interval=interval,

                                  save_count=50)



    # remove x and y - axis labels, numbers and ticks

    ax.axes.xaxis.set_ticklabels()

    ax.axes.yaxis.set_ticklabels()

    plt.xticks()

    plt.yticks()



    # plot the animated output

    plt.show()



if __name__ == '__main__':

    main()

    print("DONE")