This tutorial is part of a series. Make sure to check out the previous tutorial, if you haven't already.
In this tutorial, we will add a functionality to the Tic-Tac-Toe game: Player vs Computer 👀
Logic in Tic-Tac-Toe 🎮
Let's go ahead and create a function for the computer to determine the moves in this game.
def auto_play(): Before completing the code, let's take a look at the logic 🤔:
1. When the game can be won on the next move, either by the computer or the player
When the game can be won on the next move by computer, the move should be done. If the game can be won by player on the next move, the best option is to prevent it. It can be implemented in Python as:
# If winning of computer is possible on the next move, go ahead and win the game for winning_possibility in winning_possibilities: winning_possibility.check('O') # Check how many conditions for winning of computer are satisfied if winning_possibility.p1_satisfied and winning_possibility.p2_satisfied: # If condition 1 and 2 are satisfied, satisfy condition 3 for point in XO_points: if point.x == winning_possibility.x3 and point.y == winning_possibility.y3 and point not in X_points + O_points: # Find the point that needs to be occupied to satisfy condtion 3 and make sure that it is not already occupied point.set() # Occupy point return # End the function elif winning_possibility.p2_satisfied and winning_possibility.p3_satisfied: # If condition 2 and 3 are satisfied, satisfy condition 1 for point in XO_points: if point.x == winning_possibility.x1 and point.y == winning_possibility.y1 and point not in X_points + O_points: # Find the point that needs to be occupied to satisfy condition 1 and make sure that it is not already occupied point.set() # Occupy point return # End the function elif winning_possibility.p3_satisfied and winning_possibility.p1_satisfied: # If condition 1 and 3 are satisfied, satisfy condition 2 for point in XO_points: if point.x == winning_possibility.x2 and point.y == winning_possibility.y2 and point not in X_points + O_points: # Find the point that needs to be occupied to satisfy condition 2 and make sure that it is not already occupied point.set() # Occupy point return # End the function # If the player might win on the next move, prevent it for winning_possibility in winning_possibilities: winning_possibility.check('X') # Check how many conditions for winning of player are satisfied if winning_possibility.p1_satisfied and winning_possibility.p2_satisfied: # If condition 1 and 2 are satisfied, prevent condition 3 from being satisfied for point in XO_points: if point.x == winning_possibility.x3 and point.y == winning_possibility.y3 and point not in X_points + O_points: # Find the point and make sure that it is not already occupied point.set() # Occupy point return # End function elif winning_possibility.p2_satisfied and winning_possibility.p3_satisfied: # If condition 2 and 3 are satisfied, prevent condition 1 from being satisfied for point in XO_points: if point.x == winning_possibility.x1 and point.y == winning_possibility.y1 and point not in X_points + O_points: # Find the point and make sure that it is not already occupied point.set() # Occupy point return # End function elif winning_possibility.p3_satisfied and winning_possibility.p1_satisfied: # If condition 1 and 3 are satisfied, prevent condition 2 from being satisfied for point in XO_points: if point.x == winning_possibility.x2 and point.y == winning_possibility.y2 and point not in X_points + O_points: # Find the point and make sure that it is not already occupied point.set() # Occupy point return # End function Some changes to function "check" in class "WinningPossibility"
To check how many conditions are currently satisfied to win the game, we need to make variables p1_satisfied, p2_satisfied and p3_satisfied accessible outside the function. So, let's rename them as self.p1_satisfied, self.p2_satisfied and self.p3_satisfied respectively. The new code for the function would be:
def check(self, for_chr): self.p1_satisfied = False self.p2_satisfied = False self.p3_satisfied = False if for_chr == 'X': for point in X_points: if point.x == self.x1 and point.y == self.y1: self.p1_satisfied = True elif point.x == self.x2 and point.y == self.y2: self.p2_satisfied = True elif point.x == self.x3 and point.y == self.y3: self.p3_satisfied = True elif for_chr == 'O': for point in O_points: if point.x == self.x1 and point.y == self.y1: self.p1_satisfied = True elif point.x == self.x2 and point.y == self.y2: self.p2_satisfied = True elif point.x == self.x3 and point.y == self.y3: self.p3_satisfied = True return all([self.p1_satisfied, self.p2_satisfied, self.p3_satisfied]) 2. If center is not currently occupied
It's a good idea to occupy the center if it's not currently occupied. It can be implemented in Python as:
center_occupied = False for point in X_points + O_points: # Check if center is already occupied if point.x == 2 and point.y == 2: center_occupied = True break if not center_occupied: # If center is not occupied for point in XO_points: if point.x == 2 and point.y == 2: point.set() # Occupy center return # End the function 3. If the center is already occupied, and currently there is no winning possibility
In this case, we need to occupy either a corner point or a middle one. If fewer than two corners are occupied by the player, "O" must try to occupy the rest. If 2 or more corners are occupied by the player, it is safer to occupy the middle points instead. This can be implemented in Python as:
corner_points = [(1, 1), (1, 3), (3, 1), (3, 3)] middle_points = [(1, 2), (2, 1), (2, 3), (3, 2)] num_of_corner_points_occupied_by_X = 0 for point in X_points: # Iterate over all points occupied by the player if (point.x, point.y) in corner_points: num_of_corner_points_occupied_by_X += 1 if num_of_corner_points_occupied_by_X >= 2: # If two or more corner points are occupied by the player for point in XO_points: if (point.x, point.y) in middle_points and point not in X_points + O_points: # Find a middle point and make sure that it is not already occupied point.set() # Occupy the point return # End the function elif num_of_corner_points_occupied_by_X < 2: # If less than two corner points are occupied by the player for point in XO_points: if (point.x, point.y) in corner_points and point not in X_points + O_points: # Find a corner point and make sure that it is not already occupied point.set() # Occupy the point return # End the function Combining all code, let's write the function auto_play:
def auto_play(): # If winning is possible in the next move for winning_possibility in winning_possibilities: winning_possibility.check('O') if winning_possibility.p1_satisfied and winning_possibility.p2_satisfied: for point in XO_points: if point.x == winning_possibility.x3 and point.y == winning_possibility.y3 and point not in X_points + O_points: point.set() return elif winning_possibility.p2_satisfied and winning_possibility.p3_satisfied: for point in XO_points: if point.x == winning_possibility.x1 and point.y == winning_possibility.y1 and point not in X_points + O_points: point.set() return elif winning_possibility.p3_satisfied and winning_possibility.p1_satisfied: for point in XO_points: if point.x == winning_possibility.x2 and point.y == winning_possibility.y2 and point not in X_points + O_points: point.set() return # If the opponent can win in the next move for winning_possibility in winning_possibilities: winning_possibility.check('X') if winning_possibility.p1_satisfied and winning_possibility.p2_satisfied: for point in XO_points: if point.x == winning_possibility.x3 and point.y == winning_possibility.y3 and point not in X_points + O_points: point.set() return elif winning_possibility.p2_satisfied and winning_possibility.p3_satisfied: for point in XO_points: if point.x == winning_possibility.x1 and point.y == winning_possibility.y1 and point not in X_points + O_points: point.set() return elif winning_possibility.p3_satisfied and winning_possibility.p1_satisfied: for point in XO_points: if point.x == winning_possibility.x2 and point.y == winning_possibility.y2 and point not in X_points + O_points: point.set() return # If the center is free... center_occupied = False for point in X_points + O_points: if point.x == 2 and point.y == 2: center_occupied = True break if not center_occupied: for point in XO_points: if point.x == 2 and point.y == 2: point.set() return # Occupy corner or middle based on what opponent occupies corner_points = [(1, 1), (1, 3), (3, 1), (3, 3)] middle_points = [(1, 2), (2, 1), (2, 3), (3, 2)] num_of_corner_points_occupied_by_X = 0 for point in X_points: if (point.x, point.y) in corner_points: num_of_corner_points_occupied_by_X += 1 if num_of_corner_points_occupied_by_X >= 2: for point in XO_points: if (point.x, point.y) in middle_points and point not in X_points + O_points: point.set() return elif num_of_corner_points_occupied_by_X < 2: for point in XO_points: if (point.x, point.y) in corner_points and point not in X_points + O_points: point.set() return Creating a button to toggle play with a computer or play with a human
Let’s create a button that can switch opponents as either human or computer, as well as make a callback to change the toggle button text and command.
play_with = "Computer" def play_with_human(): global play_with play_with = "Human" # switch opponent to human play_with_button['text'] = "Play with computer" # switch text play_with_button['command'] = play_with_computer # switch command so that the user can play with the computer again, if required play_again() # restart game def play_with_computer(): global play_with play_with = "Computer" # switch opponent to computer play_with_button['text'] = "Play with human" # switch text play_with_button['command'] = play_with_human # switch command so that the user can play with a human again, if required play_again() # restart game play_with_button = tk.Button(root, text='Play with human', font=('Ariel', 15), command=play_with_human) play_with_button.pack() We need to call the function auto_play whenever it's O's turn and the value of play_with is "Computer". For this, append the following code to the function set in class XOPoint:
if play_with == "Computer" and status_label['text'] == "O's turn": auto_play() Result
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Full code in GitHub repository: https://github.com/Jothin-kumar/tic-tac-toe/
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