Variable scope

import random

CELLS = [(0, 0), (0, 1), (0, 2),
         (1, 0), (1, 1), (1, 2),
         (2, 0), (2, 1), (2, 2)]


def get_locations():
  monster = random.choice(CELLS)
  door = random.choice(CELLS)
  start = random.choice(CELLS)

  if monster == door or monster == start or door == start:
    return get_locations()

  return monster, door, start


def move_player(move):
  # pos = (x, y)
  x, y = player

  if move == 'LEFT':
    y -= 1
  elif move == 'RIGHT':
    y += 1
  elif move == 'UP':
    x -= 1
  elif move == 'DOWN':
    x += 1

  return x, y


def get_moves():
  moves = ['LEFT', 'RIGHT', 'UP', 'DOWN']
  # pos = (x, y)

  if player[1] == 0:
    moves.remove('LEFT')
  if player[1] == 2:
    moves.remove('RIGHT')
  if player[0] == 0:
    moves.remove('UP')
  if player[0] == 2:
    moves.remove('DOWN')

  return moves


def draw_map():
  print(' _ _ _')
  tile = '|{}'

  for idx, cell in enumerate(CELLS):
    if idx in [0, 1, 3, 4, 6, 7]:
      if cell == player:
        print(tile.format('X'), end='')
      else:
        print(tile.format('_'), end='')
    else:
      if cell == player:
        print(tile.format('X|'))
      else:
        print(tile.format('_|'))

monster, door, player = get_locations()
print("Welcome to the dungeon!")

while True:
  moves = get_moves()

  print("You're currently in room {}".format(player))

  draw_map()

  print("You can move {}".format(moves))
  print("Enter QUIT to quit")

  move = input("> ")
  move = move.upper()

  if move == 'QUIT':
    break

  if move in moves:
    player = move_player(move)
  else:
    print("** Walls are hard, stop walking into them! **")
    continue

  if player == door:
    print("You escaped!")
    break
  elif player == monster:
    print("You were eaten by the grue!")
    break