tictactoe.py

import random

def display_board(board):
    print(board[0] + "|" + board[1] + "|" + board[2])
    print("------")
    print(board[3] + "|" + board[4] + "|" + board[5])
    print("------")
    print(board[6] + "|" + board[7] + "|" + board[8])

def player_input(first_move):
    while 1:
        m = input(f'Player {first_move} picks first.  Would you like X or O?')
        if m in 'XO':
            break
        print("Sorry, that is not a valid input! Try again")

    marker = [' ',' ']
    marker[first_move-1] = m
    marker[2-first_move] = 'O' if m=='X' else 'X'

    print(f"Player 1 is {marker[0]} and Player 2 is {marker[1]}")
    return marker

def place_marker(board, marker):
    while 1:
        position = input(f"{marker}: Where would you like to place the marker? (1 - 9): ")
        if position.isdigit():
            position = int(position)
            if position in range(1,10):
                break
        print("Invalid input")
    
    board[position-1] = marker

def choose_first():
    first_move = random.randint(1,2)
    if first_move == 1:
        print("Player 1 (Left) will go first!")
    else:
        print("Player 2 (Right) will go first!")
    return first_move

def full_board_check(board):
    return all(b != ' ' for b in board)
    
def replay():
    while play_again not in 'yn':
        play_again = input("Would you like to play again? y or n: ")
    return play_again=='y'

def win_check(board, marker):
    return (board[0] == board[1] == board[2] == marker) or \
        (board[3] == board[4] == board[5] == marker) or \
        (board[6] == board[7] == board[8] == marker) or \
        (board[0] == board[3] == board[6] == marker) or \
        (board[1] == board[4] == board[7] == marker) or \
        (board[2] == board[5] == board[8] == marker) or \
        (board[0] == board[4] == board[8] == marker) or \
        (board[2] == board[4] == board[6] == marker)

def game():

    board = [" "," "," "," "," "," "," "," "," "]
    display_board(board)
    print("Welcome to Tic Tac Toe")

    #Choose with player will go first
    move = choose_first()

    #Ask player1 if they want to be X or O?
    marker1, marker2 = player_input(move)

    #start game
    while not full_board_check(board):
        marker = [marker1,marker2][move-1]
        place_marker(board,marker)
        display_board(board)

        if win_check(board, marker):
            print(f"Player {marker} has won!")
            break
        if full_board_check(board) == 1:
            print("Game has tied!")
            break

        move = 3-move
                    
while 1:
    game()
    if not replay():
        break
        
print("Thank you for playing!")