Dungeon game extra credit task - why use dictionary?

import random

#default grid
grid_size = 3

print("Welcome to the Dungeon Game!\n\nThere's a monster hiding in one of the rooms, and a door to escape "
    "from the dungeon in another room.\nTry to escape before the monster eats you")

def show_menu():
    menu_choice = input('\nChoose one of the following options (type word in caps in menu item)'
        '\n\n1.\tPLAY now'
        '\n2.\tChange GRID settings (default is a 3 by 3 grid)'
        '\n3.\tChange MONSTER settings (default is a static monster)'
        '\n\nQ.\tQUIT\n\n> ').lower()
    return menu_choice

def setup_grid(grid_size):
    grid = []
    for idx_x in list(range(grid_size)):
        for idx_y in list(range(grid_size)):
            coords = idx_x, idx_y
            grid.append(coords)
    return grid

def assign_start_pos(grid):
    player_pos = random.choice(grid)
    monster_pos = random.choice(grid)
    door_pos = random.choice(grid)
    if player_pos is monster_pos or player_pos is door_pos or monster_pos is door_pos:
        return assign_start_pos(grid)
    #print('{}{}{}'.format(player_pos,monster_pos,door_pos))
    return player_pos, monster_pos, door_pos

def move_player(player_pos, grid_size):
    moves = ['UP', 'DOWN', 'LEFT', 'RIGHT']
    if player_pos[0] is 0:
        moves.remove('UP')
    if player_pos[0] is grid_size-1:
        moves.remove('DOWN')
    if player_pos[1] is 0:
        moves.remove('LEFT')
    if player_pos[1] is grid_size-1:
        moves.remove('RIGHT')

    move = input("\nWhat's your next move? Your possible moves are {} > ".format(moves)).upper()
    if move == 'L':
        move = 'LEFT'
    elif move == 'R':
        move = 'RIGHT'
    elif move == 'D':
        move = 'DOWN'
    elif move == 'U':
        move = 'UP'
    if move in moves:
        row, col = player_pos
        if move == 'LEFT':
            col -= 1
        if move == 'RIGHT':
            col += 1
        if move == 'UP':
            row -= 1
        if move == 'DOWN':
            row += 1
        player_pos = row, col
    elif move in ['LEFT', 'RIGHT', 'DOWN', 'UP']:
        print("\nYou've hit a wall!!")
    elif move == 'QUIT':
        player_pos = move
    else:
        print("\nPlease choose a direction")

    return player_pos

def show_grid(player_pos, player_status, grid, grid_size, prev_player_pos):
    for idx in range(grid_size):
        print('__', end='')
    print('_')
    left_wall = list(range(grid_size*grid_size))[::grid_size]
    right_wall = list(range(grid_size*grid_size))[grid_size-1::grid_size]
    for idx, position in enumerate(grid):
        if idx in left_wall:
            print('|',end='')
        if position == player_pos:
            if player_status == 'ongoing':
                print('o|',end='')
            elif player_status == 'eaten':
                print('M|',end='')
            elif player_status == 'free':
                print('◊|',end='')
        elif position in prev_player_pos:
            print('.|',end='')
        else:
            print('_|',end='')
        if idx in right_wall:
            print('')

def run_game(player_pos, monster_pos, door_pos, grid_size, grid):
    player_status = 'ongoing'
    print('\nType "QUIT" at any point to leave game')
    prev_player_pos = []
    while True:
        show_grid(player_pos, player_status, grid, grid_size, prev_player_pos)
        prev_player_pos.append(player_pos)
        player_pos = move_player(player_pos, grid_size)
        if player_pos == monster_pos:
            player_status = 'eaten'
            show_grid(player_pos, player_status, grid, grid_size, prev_player_pos)
            print("\nYou've bumped into the monster unfortunately and he's devoured you")
            break
        elif player_pos == door_pos:
            player_status = 'free'
            show_grid(player_pos, player_status, grid, grid_size, prev_player_pos)
            print("\nYou've found the exit to the dungeon. You're free. The monster is still hungry!")
            break
        elif player_pos == 'QUIT':
            break
        else:
            player_status = 'ongoing'
            #show_grid(player_pos, player_status, grid, grid_size)
            #player_pos = move_player(player_pos, grid_size)

#run game until player quits, wins or loses

menu_choice = show_menu()
while True:
    if menu_choice == 'quit':
        break
    elif menu_choice == 'play':
        grid = setup_grid(grid_size)
        player_pos, monster_pos, door_pos = assign_start_pos(grid)

        run_game(player_pos, monster_pos, door_pos, grid_size, grid)

        play_again = input('\nWould you like to play again? (Yes/No) > ').lower()
        if play_again == 'yes':
            print('\n'*100)
            menu_choice = show_menu()
        else:
            menu_choice = 'quit'

    elif menu_choice == 'grid':
        while True:
            grid_size = input('\nWhat size grid do you want? (Enter one number n which will give an n x n grid) > ')
            try:
                grid_size = int(grid_size)
                break
            except:
                print('\nThe grid size must be a single integer number. Please try again…')
        #grid = setup_grid(grid_size)
        menu_choice = show_menu()
    elif menu_choice == 'monster':
        print('\nOption not available yet. Please wait for next version of game!')
        menu_choice = show_menu()
    else:
        print('\nPlease choose one of the options listed in the menu.')
        menu_choice = show_menu()

print('\nThank you for playing The Dungeon Game. Please come back soon.')