类变量引用本身？ [英] Class variable reference itself?

问题描述

我是编码阶段（3个星期）的新手，并且一直在构建和重建RPG，以帮助自己学习所学的原理。但是，我似乎只停留在Python类的一个特定方面。

I am new to coding period (3-ish weeks) and have been building and rebuilding a RPG to help teach myself the principles that I have been learning. However, I seem to be stuck on one specific aspect of Python classes.

我为 worldLocation 类的读法如下，其中 NORTH ， EAST ， SOUTH ， WEST 所有参考字符串：

A class variable I have created for my worldLocation class reads as such where the NORTH, EAST, SOUTH, WEST all reference strings:

WHITEROOM = worldLocation('A Plain White Room',
                          '...\n\nWhere are you?\n\n'
                          'All around you is white...\n\n'
                          '...only white...',
                          [ROCK.GROUNDDESC],
                          [RAT.NAME],
                          {NORTH: 'A Plain White Room',
                           SOUTH: 'A Plain White Room',
                           EAST: 'A Plain White Room',
                           WEST: 'A Plain White Room'})

但是我希望它改为这样，其中每个实例变量都引用了e类变量本身：

But I want it to instead read like this, where each of the instance variables references the class variable itself:

WHITEROOM = worldLocation('A Plain White Room',
                          '...\n\nWhere are you?\n\n'
                          'All around you is white...\n\n'
                          '...only white...',
                          [ROCK.GROUNDDESC],
                          [RAT.NAME],
                          {NORTH: WHITEROOM,
                           SOUTH: WHITEROOM,
                           EAST: WHITEROOM,
                           WEST: WHITEROOM})

但是，每次我尝试将其更改为后者时，都会收到未定义名称WHITEROOM 错误。我在做什么错还是想念？

However, every time I attempt to change it to the latter, I receive an undefined name WHITEROOM error. What am I doing wrong or missing?

课程代码如下：

class worldLocation(object):
    def __init__(self, NAME, DESC, GROUND, ENEMIES, DIRECTIONS):
        self.NAME = NAME
        self.DESC = DESC
        self.GROUND = GROUND
        self.ENEMIES = ENEMIES
        self.DIRECTIONS = DIRECTIONS

推荐答案

您要使用的代码试图引用字典中的实例作为参数传递给 __ init __（） 之前存在。那是行不通的（如果考虑的话，那可能真的很合理）。

The code you want to use is trying to reference the instance in a dictionary being passed as argument to __init__() before it exists. That's not feasible (and arguably really reasonable if you think about it).

但是，您可以通过创建类初始化器<$ c $的特殊值来解决此问题。 c> __ init __（）方法可以检查并修复传递的数据。

However, you can workaround the issue by creating a special value that the class initializer __init__() method can check for and fix-up the data being passed.

下面的代码说明了我的意思。 注意我在开始时添加了一些脚手架，使其可以运行以用于测试。

Below is code illustrating what I mean. Note I've added some scaffolding at the beginning to make it runnable for testing purposes.

#### Some scaffolding for testing.
NORTH, SOUTH, EAST, WEST = 'NORTH SOUTH EAST WEST'.split()

class ROCK:
    GROUNDDESC = 'ground desc'

class RAT:
    NAME = 'Ricky'
####


class WorldLocation:
    THIS = object()  # A unique value.

    def __init__(self, NAME, DESC, GROUND, ENEMIES, DIRECTIONS):
        self.NAME = NAME
        self.DESC = DESC
        self.GROUND = GROUND
        self.ENEMIES = ENEMIES

        # Replace any values in DIRECTIONS dictionary argument that refer to the
        # instance being created (as designated by them being the class
        # attribute THIS).
        self.DIRECTIONS = {direction: self if value is self.THIS else value
                               for direction, value in DIRECTIONS.items()}


WHITEROOM = WorldLocation('A Plain White Room',
                          '...\n\nWhere are you?\n\n'
                          'All around you is white...\n\n'
                          '...only white...',
                          [ROCK.GROUNDDESC],
                          [RAT.NAME],
                          {NORTH: WorldLocation.THIS,
                           SOUTH: WorldLocation.THIS,
                           EAST: WorldLocation.THIS,
                           WEST: WorldLocation.THIS})

# Show that it works.
from pprint import pprint

print(f'id(WHITEROOM): 0x{id(WHITEROOM):08x}\n')
pprint(vars(WHITEROOM))

示例输出：

id(WHITEROOM): 0x010d0390

{'DESC': '...\n'
         '\n'
         'Where are you?\n'
         '\n'
         'All around you is white...\n'
         '\n'
         '...only white...',
 'DIRECTIONS': {'EAST': <__main__.WorldLocation object at 0x010D0390>,
                'NORTH': <__main__.WorldLocation object at 0x010D0390>,
                'SOUTH': <__main__.WorldLocation object at 0x010D0390>,
                'WEST': <__main__.WorldLocation object at 0x010D0390>},
 'ENEMIES': ['Ricky'],
 'GROUND': ['ground desc'],
 'NAME': 'A Plain White Room'}

这篇关于类变量引用本身？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！