A simplified version of the game of Nim in which a player plays against a computer player.

Nim.py

###############################################################################
#
#Computer Project #2
#
#Algorithm
#
#   Get if user wants to play the game
#   Initialize starting state variables for a new game
#   Display current amount of stones in each pile (5)
#   Until the game is won, player and computer alternate turns taking stones
#   from the piles. (Note: the computer always takes 1 stone from the opposite
#   pile that the player picked, if possible. Player can take up to 3.)
#   Display how many stones both player and computer took from a certain pile
#   Output the updated number of stones in the piles
#   After each turn, determine if the game has been won (if the last stone has
#   been taken)
#   If the game is over, determine the winner based on who took the last turn
#   Output the winner
#   Output the number of games the player and computer have won
#   Ask user if they wish to play again

###############################################################################

#Display the rules of the game

print("\nWelcome to the game of Nim! I'm probably going to win...")
print("Nim is a simple two-player game based on removing stones.\
 The game begins with two piles of stones, numbered 1 and 2.\
 Players alternate turns. Each turn, a player chooses to remove one,\
 two, or three stones from some single pile. The player who removes the\
 last stone wins the game.")

# Initialize number of times player and computer have won.
player_wins = 0
computer_wins = 0

# Ask the user if they want to play the game.
play_str=input("Would you like to play? (0=no, 1=yes) ")


while int(play_str) != 0:
    # Initialize the state for a new game.
    players_turn = True
    pile_1 = 5
    pile_2 = 5
    game_over = False
    print("Start --> Pile 1:", pile_1, "   Pile 2:", pile_2)
    
    # Continue to have the user and computer take turns until the game is over.
    # Determined by removal of all stones.
    # Note: All 'else' cases are used to handle errors, with very few 
    # exceptions.
    while game_over == False:
        
        # To allow for error handling, the user will be prompted for input
        # until a valid one is made.
        while players_turn == True:
            players_pile_choice_str = input('Choose a pile (1 or 2): ')
            # Player chooses a pile and the pile must have at least 1 stone to
            # take from that pile.
            if int(players_pile_choice_str) == 1:
                if pile_1 > 0:
                    # Remove a number of stones chosen by user as long as the
                    # pile has at least that many left to take.
                    remove_stones_str = input('Choose stones to remove \
from pile: ')
                    if int(remove_stones_str) <= pile_1:
                        print("Player -> Remove", remove_stones_str, "stones \
from pile 1")
                        pile_1 -= int(remove_stones_str)
                        players_turn = False    # Computer's turn.
                    
                    else:
                        # Error for removing too many stones from the pile.
                        print("Invalid number of stones. Please try again.")
                else:
                    # Error for picking a pile without stones.
                    print("Pile must be 1 or 2 and non-empty. Please try \
again.")

            elif int(players_pile_choice_str) == 2:
                if pile_2 > 0:
                     # Remove a number of stones chosen by user as long as the
                     # pile has at least that many left to take.
                    remove_stones_str = input('Choose stones to remove \
from pile: ')
                    if int(remove_stones_str) <= pile_2:
                        print("Player -> Remove", remove_stones_str, "stones \
from pile 2")
                        pile_2 -= int(remove_stones_str)
                        players_turn = False    # Computer's turn.
                    else:
                        # Error for removing too many stones from the pile.
                        print("Invalid number of stones. Please try again.")
                else:
                    # Error for picking a pile without stones.
                    print("Pile must be 1 or 2 and non-empty. Please try \
again.")
            else:
                # Error for not picking 1 or 2.
                print("Pile must be 1 or 2 and non-empty. Please try again.")
        
        
        # Check if the game should be over, now that the player has taken
        # his/her turn.
        if pile_1 == 0 and pile_2 == 0:
            game_over = True
            print("Pile 1:", pile_1, "   Pile 2:", pile_2)
            continue
        # If the game is not over, print the number of stones in each pile
        # so the user can see the remaining stones.
        else:
            print("Pile 1:", pile_1, "   Pile 2:", pile_2)
        
        
        # Computer's turn.
        if int(players_pile_choice_str) == 1:
            if pile_2 > 0:
                print("Computer -> Remove 1 stones from \
pile 2")
                pile_2 -= 1
                players_turn = True
            else:
                # Computer takes one stone from pile 1 since there are no
                # more stones in pile 2.
                print("Computer -> Remove 1 stones from \
pile 1")
                pile_1 -= 1
                players_turn = True
        
        if int(players_pile_choice_str) == 2:
            if pile_1 > 0:
                print("Computer -> Remove 1 stones from \
pile 1")
                pile_1 -= 1
                players_turn = True
            else:
                # Computer takes one stone from pile 2 since there are no
                # more stones in pile 1.
                print("Computer -> Remove 1 stones from \
pile 2")
                pile_2 -= 1
                players_turn = True
        
        # Check if the game should be over, now that the computer has taken its
        # turn.
        if pile_1 == 0 and pile_2 == 0:
            game_over = True
            print("Pile 1:", pile_1, "   Pile 2:", pile_2)
        # If the game is not over, print the number of stones in each pile
        # so the user can see the remaining stones.
        else:
            print("Pile 1:", pile_1, "   Pile 2:", pile_2)
    
    # Determine winner.
    else:
        # If it is the player's turn, that means the computer just took its
        # turn, taking the last stone, and ending the game. Therefore, it must 
        # have won.
        if players_turn == True:
            computer_wins += 1
            print("\nComputer wins!")
            print("Score -> human:", player_wins, "; computer:", computer_wins)
            play_str = input("\nWould you like to play again? (0=no, 1=yes) ")
        
        # If it is not the player's turn, that means the player just took
        # his/her turn, taking the last stone, and ending the game. Therefore,
        # he/she must have won.
        if players_turn == False:
            player_wins += 1
            print("\nPlayer wins!")
            print("Score -> human:", player_wins, "; computer:", computer_wins)
            play_str = input("\nWould you like to play again? (0=no, 1=yes) ")

# Display to the user that the game has officially ended.
else:
   print("\nThanks for playing! See you again soon!")