AttributeError：“ NoneType”对象没有属性“ intro_text”

Question

我对编码还很陌生，并且一直在《 Make Your Own Python Text Adventure》一书的帮助下尝试使用Python 3编写文本冒险程序。但是，当我尝试以当前状态运行游戏时，仍然会收到AttributeError: 'NoneType' object has no attribute 'intro_text'。

如果玩家移出设置区域（因为尚没有停止该代码的代码），应该会发生这种情况，但是它总是在初始化时发生，这是不应该的。根据本书的建议，我尝试查看世界的“地图”和Player类的起点，但看不到错误。我希望有人的编码眼睛比我能提供的帮助更大。

这是game.py：

from player import Player
import world


def play():
    print("Escape from Cave Terror!")
    player = Player()
    while True:
        room = world.tile_at(player.x, player.y)
        print(room.intro_text())
        action_input = get_player_command()
        if action_input in ['n', 'N']:
            player.move_north()
        elif action_input in ['s', 'S']:
            player.move_south()
        elif action_input in ['e', 'E']:
            player.move_east
        elif action_input in ['w', 'W']:
            player.move_west()
        elif action_input in ['i', 'I']:
            player.print_inventory()
        elif action_input in ['q', 'Q']:
            exit()
        else:
            print("Invalid action!")


def get_player_command():
    return input('Action: ')


play()

这是来自player.py：

import items


class Player:
        def __init__(self):
            self.inventory = [items.Rock(),
            items.Dagger(),
            'Gold(5)',
            'Crusty Bread']

            self.x = 1
            self.y = 2

        def print_inventory(self):
            print('Inventory: ')
            for item in self.inventory:
                print('*' + str(item))
            best_weapon = self.most_powerful_weapon()
            print('Your best weapon is your {}'.format(best_weapon))

        def most_powerful_weapon(self):
            max_damage = 0
            best_weapon = None
            for item in self.inventory:
                try:
                    if item.damage > max_damage:
                        best_weapon = item
                        max_damage = item.damage
                except AttributeError:
                    pass

            return best_weapon

        def move(self, dx, dy):
            self.x += dx
            self.y += dy

        def move_north(self):
            self.move(dx=0, dy=-1)

        def move_south(self):
            self.move(dx=0, dy=1)

        def move_east(self):
            self.move(dx=1, dy=0)

        def move_west(self):
            self.move(dx=-1, dy=0)

这是world.py：

class MapTile:
    def __init__(self, x, y):
        self.x = x
        self.y = y

    def intro_text(self):
        raise NotImplementedError("Create a subclass instead!")


class StartTile(MapTile):
    def intro_test(self):
        return """
        You find yourself in a cave with a flickering torch on the wall.
        You can make out four paths, each equally as dark and foreboding.
        """


class BoringTile(MapTile):
    def intro_text(self):
        return """
        This is a very boring part of the cave.
        """


class VictoryTile(MapTile):
    def intro_text(self):
        return """
        You see a bright light in the distance...
        ... it grows as you get closer! It's sunlight!


        Victory is yours!
        """

world_map = [
    [None,VictoryTile(1,0),None],
    [None,BoringTile(1,1),None],
    [BoringTile(0,2),StartTile(1,2),BoringTile(2,2)],
    [None,BoringTile(1,3),None]
]

def tile_at(x, y):
    if x < 0 or y < 0:
        return None
        try:
            return world_map[y][x]
        except IndexError:
            return None

我收到错误而不是起始房间信息：

Escape from Cave Terror!
Traceback (most recent call last):
  File "game.py", line 32, in <module>
    play()
File "game.py", line 10, in play
    print(room.intro_text())
AttributeError: 'NoneType' object has no attribute 'intro_text'