PyYAML与组合，属性错误

Question

我一直在努力掌握 PyYAML，因为我喜欢它的可读性，并且想在我工作的几个开源项目中使用它作为 JSON 的替代品。

但是，我正在努力理解如何使用组合来构造对象。我打开了这个问题：它似乎在读出信息方面有效，但在完整程序的上下文中无效。

这是我尝试进行 YAMLify 的精简示例：

import yaml
import data

class DungeonObject(yaml.YAMLObject):
    yaml_tag = u'!DungeonObject'
    def __init__(self, x, y, char, name, blocks=False, fighter=None):
        self.x = x
        self.y = y
        self.char = char
        self.name = name
        self.blocks = blocks

        self.fighter = fighter
        if self.fighter:
            self.fighter.owner = self


    def __repr__(self):
        return "%s(x=%r, y=%r, char=%r, name=%r, blocks=%r fighter=%r)" % (self.__class__.__name__, self.x, self.y, self.char, self.name, self.blocks, self.fighter)

class Fighter(yaml.YAMLObject):
    yaml_tag = u'!Fighter'
    #combat-related properties and methods (monster, player, NPC).
    def __init__(self, hp, defense, strength):
        self.hp = hp
        self.base_defense = defense
        self.base_strength = strength
    def __repr__(self):
        return "%s(hp=%r, defense=%r, strength=%r)" % (self.__class__.__name__, self.hp, self.defense, self.strength)


monsters = {DungeonObject.name : DungeonObject for DungeonObject in yaml.load_all(data.monsterdata)}
print (monsters)

还有我的 YAML 文件：

monsterdata = """
---
!Fighter &fighter_component
    hp: 20
    defense: 0
    strength: 4
!DungeonObject
    x: x
    y: y
    char: 'o'
    name: 'orc'
    blocks: True
    fighter: fighter_component
---
!Fighter &fighter_component
    hp: 9
    defense: 0
    strength: 10
!DungeonObject
    x: x
    y: y
    char: 't'
    name: 'troll'
    blocks: True
    fighter: fighter_component
"""

有了这个，我得到了错误： 第 32 行，在 monsters = {DungeonObject.name : yaml.load_all(data.monsterdata) 中的 DungeonObject 的 DungeonObject AttributeError: 'Fighter' 对象没有属性 'name'

Answer 1

每个文档都应包含一个 sequence/list，其中包含一个 Fighter 和一个 DungeonObject。前者没有名称，因此您应该过滤实际属于 DungeonObject 类型而不是 Fighter 类型的 DungeonObjects。

有点令人困惑的是您还使用了一个变量 DungeonObject，因此尝试对变量使用 dungeon_object：

from ruamel import yaml

monsterdata = """
---
- !Fighter &fighter_component
    hp: 20
    defense: 0
    strength: 4
- !DungeonObject
    x: x
    y: y
    char: 'o'
    name: 'orc'
    blocks: True
    fighter: fighter_component
---
- !Fighter &fighter_component
    hp: 9
    defense: 0
    strength: 10
- !DungeonObject
    x: x
    y: y
    char: 't'
    name: 'troll'
    blocks: True
    fighter: fighter_component
"""


class DungeonObject(yaml.YAMLObject):
    yaml_tag = u'!DungeonObject'

    def __init__(self, x, y, char, name, blocks=False, fighter=None):
        self.x = x
        self.y = y
        self.char = char
        self.name = name
        self.blocks = blocks

        self.fighter = fighter
        if self.fighter:
            self.fighter.owner = self

    def __repr__(self):
        return "{}(x={!r}, y={!r}, char={!r}, name={!r}, blocks={!r} fighter={!r})".format(
            self.__class__.__name__, self.x, self.y, self.char, self.name,
            self.blocks, self.fighter)


class Fighter(yaml.YAMLObject):
    yaml_tag = u'!Fighter'
    # combat-related properties and methods (monster, player, NPC).

    def __init__(self, hp, defense, strength):
        self.hp = hp
        self.base_defense = defense
        self.base_strength = strength

    def __repr__(self):
        return "{}(hp={!r}, defense={!r}, strength={!r})".format(
            self.__class__.__name__, self.hp, self.defense, self.strength)

monsters = {}
for doc in yaml.load_all(monsterdata, Loader=yaml.Loader):
    for dungeon_object in doc:
        if isinstance(dungeon_object, DungeonObject):
            monsters[dungeon_object.name] = dungeon_object

print (monsters)

给出：

{'orc': DungeonObject(x='x', y='y', char='o', name='orc', blocks=True fighter='fighter_component'), 'troll': DungeonObject(x='x', y='y', char='t', name='troll', blocks=True fighter='fighter_component')}

我更新了 __repr__ 以使用更现代的 .format() 方法。由于我使用的是 ruamel.yaml（它是 PyYAML 功能的超集并且向后兼容），因此我需要明确指定加载程序以抑制使用默认加载程序时 load_all 不安全的警告。（免责声明：我是那个包的开发者）

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