問題描述

如果用戶在字典中輸入重復(fù)鍵，我會嘗試引發(fā)錯誤.字典在一個文件中，用戶可以手動編輯該文件.

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',...},
              }
      }

新鍵a"已經(jīng)存在...

the new key 'a' already exist...

當(dāng)我從文件中加載 dico 時，如何測試 dico 并警告用戶?

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

推薦答案

寫一個dict的子類，覆蓋__setitem__，這樣在替換現(xiàn)有key時會拋出錯誤；重寫文件以使用新子類的構(gòu)造函數(shù)而不是默認(rèn)的 dict 內(nèi)置函數(shù).

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)

那么你的文件必須寫成

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')
        ),

        ....
    )
)

使用元組而不是字典來導(dǎo)入文件(使用 {} 表示法編寫，它將使用默認(rèn)的字典構(gòu)造函數(shù)，并且重復(fù)項會在字典構(gòu)造函數(shù)獲取它們之前消失！).

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!).

這篇關(guān)于如果字典中的鍵重復(fù)，如何引發(fā)錯誤的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網(wǎng)！