如果字典中的键重复，如何引发错误

How to raise error if duplicates keys in dictionary(如果字典中的键重复，如何引发错误)

问题描述

如果用户在字典中输入重复键，我会尝试引发错误.字典在一个文件中，用户可以手动编辑该文件.

I try to raise an error if the user enter a duplicate key in a dictionary. The dictionary is in a file and the user can edit the file manually.

例子:

dico= {'root':{
                'a':{'some_key':'value',...},
                'b':{'some_key':'value',...},
                'c':{'some_key':'value',...},
                ...

                'a':{'some_key':'value',...},
              }
      }

新键a"已经存在...

the new key 'a' already exist...

当我从文件中加载 dico 时，如何测试 dico 并警告用户?

How can I test dico and warn the user when I load dico from the file?

推荐答案

写一个dict的子类，覆盖__setitem__，这样在替换现有key时会抛出错误；重写文件以使用新子类的构造函数而不是默认的 dict 内置函数.

Write a subclass of dict, override __setitem__ such that it throws an error when replacing an existing key; rewrite the file to use your new subclass's constructor instead of the default dict built-ins.

import collections

class Dict(dict):
    def __init__(self, inp=None):
        if isinstance(inp,dict):
            super(Dict,self).__init__(inp)
        else:
            super(Dict,self).__init__()
            if isinstance(inp, (collections.Mapping, collections.Iterable)): 
                si = self.__setitem__
                for k,v in inp:
                    si(k,v)

    def __setitem__(self, k, v):
        try:
            self.__getitem__(k)
            raise ValueError("duplicate key '{0}' found".format(k))
        except KeyError:
            super(Dict,self).__setitem__(k,v)

那么你的文件必须写成

dico = Dict(
    ('root', Dict(
        ('a', Dict(
            ('some_key', 'value'),
            ('another_key', 'another_value')
        ),
        ('b', Dict(
            ('some_key', 'value')
        ),
        ('c', Dict(
            ('some_key', 'value'),
            ('another_key', 'another_value')
        ),

        ....
    )
)

使用元组而不是字典来导入文件(使用 {} 表示法编写，它将使用默认的字典构造函数，并且重复项会在字典构造函数获取它们之前消失！).

using tuples instead of dicts for the file import (written using the {} notation, it would use the default dict constructor, and the duplicates would disappear before the Dict constructor ever gets them!).

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