python - dict.fromkeys 是否会一遍又一遍地分配相同的引用？

Question

我尝试创建满足我需要的完美字典(包含带有值和列表的字典的字典)。然而，我似乎一遍又一遍地分配相同的引用。

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

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

结果如下:

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

如您所见，val1、val2 和 val3 引用同一个字典。我不知道我应该如何处理？有什么建议吗？

Answer 1

这种事情通常用dictionary comprehensions来完成。而不是dict.fromkeys():

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

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

输出:

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