Problems with Conway's Game of Life

Question

I am stuck with a problem that I haven't been successful in finding the solution through other people's post. We are following standard rules for Conway's Game of Life.

So far I have been able to create the 2d array as well as populate the array with a random character of '-' for dead and 'O' for alive (The letter O not the number zero). I believe that I am going through and checking all of the neighbors correctly. * The reason I used try/catch is because it was the only way I could figure out how to avoid getting an out of bounds error message.

My main issue is that I'm not sure if I am going through the array correctly when checking/changing values. Also I am not sure how to go about printing the "updated" 2d array after applying the live/die rules to the entire array.

As of right now, the output prints the randomized array once, then prints the exact same array again, then asks if i want to continue ( Go through the while loop again). If I choose 'y', I get the error message

TypeError: list indices must be integers, not list

I'm beyond lost, any ideas will help as I am about 3 weeks into python.

Here is my code:

import random

numrows = 25
numcols = 25


def rnd():
    rn = random.randint(0,1)
    return rn


def initial():

    grid = []
    count = 0

    for x in range(numrows):
        grid.append([])
        for y in range(numcols):
            rand=random.randrange(1,3)
            if(rand == 1):
                grid[x].append('O')
            else:
                grid[x].append('-')

    for x in grid:    
        print(*x, sep=' ',end="\n") #prints initial grid with random values

    print("")# space for clarity sake
    print("")#      "       "

    answer = 'y'
    count = 0

    while(answer == 'y'):

        #This is where I am checking each neighbor. Adding 1 to count for each
        #live neighbor.

        for r in range(0,numrows):
            for c in range(0,numcols):


                try:
                    if(grid[r-1][c-1] == 'O'):
                        count += 1

                except:
                    pass

                try:
                    if(grid[r-1][c] == 'O'):
                        count += 1

                except:
                    pass

                try:
                    if(grid[r-1][c+1] == 'O'):
                        count += 1

                except:
                    pass

                try:
                    if(grid[r][c-1] == 'O'):
                        count += 1

                except:
                    pass

                try:

                    if(grid[r][c+1] == 'O'):
                        count += 1

                except:
                    pass

                try:
                    if(grid[r+1][c-1] == 'O'):
                        count += 1

                except:
                    pass

                try:
                    if(grid[r+1][c] == 'O'):
                        count += 1

                except:
                    pass

                try:
                    if(grid[r+1][c+1] == 'O'):
                        count += 1

                except:
                    pass


                #this is where I am applying the rules of living or dying
                #based on how many neighbors there are.

                if(grid[r][c] == '-'):
                        if(count == 3):
                            grid[r][c].append('O')

                if(grid[r][c] == 'O'):
                    if(count < 2):
                        grid[r][c].append('-')

                if(grid[r][c] == 'O'):
                    if(count == 2 or count == 3):
                        grid[r][c].append('O')

                if(grid[r][c] == 'O'):
                    if(count > 3):
                        grid[r][c].append('-')

                for r in grid:                 #This is a problem area as i dont
                    print(*r, sep=' ',end="\n")#know how to print the grid 

                answer = input("Continue? y or n( lower case only): ")

                if(answer != 'y'):
                    print(" Hope you had a great life! Goodbye!")

Answer 1

Here is the problem: the crash occurs at the if line:

                if(grid[r][c] == '-'):  # <=== here on this line
                        if(count == 3):
                            grid[r][c].append('O')

On that line, r is no longer an integer, but it is a list. But, why? The answer occurs a few lines later:

            for r in grid:                 #This is a problem area as i dont
                print(*r, sep=' ',end="\n")#know how to print the grid

In this block, r was an int, but now you turned it into a list. I acknowledge your comment there, on not knowing how to print the grid, so may I suggest a quickie:

print('\n'.join(' '.join(str(cell) for cell in row) for row in grid))

This way, you are not overwriting the variable r.