dict.fromkeys是否分配相同的引用？ [英] Does dict.fromkeys assign the same reference over and over?

问题描述

我试图为我的需要创建完美的字典（dict包含一个含有值和列表的dict）。但是，似乎我一遍又一遍地分配了相同的引用。

  brands = ['val1'，'val2'，'val3 '] 
 infoBrands = dict.fromkeys（品牌，
 dict（dict.fromkeys（['nbOffers'，'nbBestOffers']，0），
 ** dict.fromkeys（['higherPrice ']，[]）））
 
 infoBrands ['val1'] ['nbOffers'] + = 1 
打印infoBrands 
  

这里结果：

  {'val3'：
 {'higherPrice'：[]，
'nbOffers'：1，
'nbBestOffers'：0}，
'val2'：
 {'higherPrice'：[]，
'nbOffers'：1，
'nbBestOffers'：0}，
'val1'：
 {'higherPrice'：[]，
'nbOffers'：1，
'nbBestOffers'：0} 
} 
  

你可以看到，val1，val2和val3指的是同一个dict。
我不知道该怎么处理它？
任何提示？

解决方案

这种事情通常用 字典理解 ，而不是 dict.fromkeys（）：

  brands = ['val1'，'val2'，'val3 '] 
 infoBrands = {brand：{'nbOffers'：0，'nbBestOffers'：0，'higherPrice'：[]}品牌品牌的
} 
 
 infoBrands [ 'val1'] ['nbOffers'] + = 1 
打印infoBrands 
  

输出： / p>

  {'val3'：{'higherPrice'：[]，'nbOffers'：0， nbBestOffers'：0}，
'val2'：{'higherPrice'：[]，'nbOffers'：0，'nbBestOffers'：0}，
'val1'：{'higherPrice' ，'nbOffers'：1，'nbBestOffers'：0}} 
  

I tried to create the perfect dictionary for my needs (dict that's containing a dict with values and a list). However it seems that I assigned the same reference over and over.

brands = ['val1', 'val2', 'val3']
infoBrands = dict.fromkeys(brands,
                dict(dict.fromkeys(['nbOffers', 'nbBestOffers'], 0),
                     **dict.fromkeys(['higherPrice'], [])))

infoBrands['val1']['nbOffers'] += 1
print infoBrands

Here the results:

{'val3':
     {'higherPrice': [],
       'nbOffers': 1,
       'nbBestOffers': 0},
  'val2':
       {'higherPrice': [],
        'nbOffers': 1,
        'nbBestOffers': 0},
  'val1':
       {'higherPrice': [],
        'nbOffers': 1,
        'nbBestOffers': 0}
}

As you can see, val1, val2 and val3 refer to the same dict. I'm not sure how I should handle it? Any tips?

解决方案

This sort of thing is commonly done with dictionary comprehensions rather thandict.fromkeys():

brands = ['val1', 'val2', 'val3']
infoBrands = {brand: {'nbOffers': 0, 'nbBestOffers': 0, 'higherPrice': []}
                for brand in brands}

infoBrands['val1']['nbOffers'] += 1
print infoBrands

Output:

{'val3': {'higherPrice': [], 'nbOffers': 0, 'nbBestOffers': 0},
 'val2': {'higherPrice': [], 'nbOffers': 0, 'nbBestOffers': 0},
 'val1': {'higherPrice': [], 'nbOffers': 1, 'nbBestOffers': 0}}

这篇关于dict.fromkeys是否分配相同的引用？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！