Tic-Tac-Toe

tic_tac_toe.py

"""Tic-Tac-Toe

A simple implementation in (mostly) procedural style.
"""

import sys
from random import choice
from typing import TypeAlias

Board: TypeAlias = list[list[str]]


def display_board(grid: Board) -> None:
    """Display the board."""
    print("  1  2  3")
    for row_num, row in enumerate(grid):
        print(row_num + 1, end='')
        for cell in row:
            print(f"[{cell}]", end='')
        print()
    print()


def get_empty_cells(grid: Board) -> list[tuple[int, int]]:
    """Return list of empty cell coordinates."""
    return [(r_idx, c_idx) for r_idx, row in enumerate(grid)
            for c_idx, char in enumerate(row)
            if char == '_']


def player_turn(grid: Board, char: str) -> None:
    """Add player's move to the board."""
    empty_cells = get_empty_cells(grid)
    input_requested = False
    while True:
        if input_requested:
            print("Invalid choice.")
            print("Enter row and column as numbers in range 1 to 3.")

        coords = input("row column: ").strip()
        input_requested = True

        if len(coords) == 2:  # No space
            try:
                row = int(coords[0]) - 1
                col = int(coords[1]) - 1
            except ValueError:
                continue
        else:
            try:
                row, col = [int(val) - 1 for val in coords.split()]
            except ValueError:
                continue
        if (row, col) in empty_cells:
            grid[row][col] = char
            return


def pc_turn(grid: Board, char: str) -> None:
    """Add computer's move to the board."""
    row, col = choice(get_empty_cells(grid))
    grid[row][col] = char.upper()


def is_winner(grid: Board, char: str) -> bool:
    """Return True if 'char' (O or X) has won, else False."""
    cols = [[row[col] for row in grid] for col in range(3)]
    diag1 = [[grid[i][i] for i in range(3)]]
    diag2 = [[grid[i][2 - i] for i in range(3)]]
    all_lines = grid + cols + diag1 + diag2
    return [char, char, char] in all_lines


def main() -> None:
    """Main game loop."""
    board = [['_' for _ in range(3)] for _ in range(3)]
    players = ('O', 'X')
    player = choice(players)
    pc = 'X' if player == 'O' else 'O'

    print("Let's play Tic-Tac-Toe.")
    print(f"You are {player}'s")
    print("\nSelect your position as \"row column\", where")
    print("row and column are numbers 1 to 3.\n")

    while get_empty_cells(board):
        pc_turn(board, pc)
        display_board(board)
        if is_winner(board, pc):
            print("You lost")
            return

        if not get_empty_cells(board):
            break

        player_turn(board, player)
        display_board(board)
        if is_winner(board, player):
            print("You won")
            return
    print("Draw")


if __name__ == '__main__':
    try:
        main()
    except (KeyboardInterrupt, EOFError):
        sys.exit("Bye")