我有一个结构如下的dict products
:
{'Cheese': {'Cheese': {'comment': 'Markets quiet this week', 'indicator': 'Flat', 'pricelow': '3385', 'priceaverage': '3385', 'pricehigh': '3385'}}, 'MPC': {'MPC70': {'comment': 'Large buyers', 'indicator': 'Flat', 'pricelow': '8598', 'priceaverage': '8929', 'pricehigh': '9039'}, 'MPI:': {'comment': 'Large buyers', 'indicator': 'Flat', 'pricelow': '8598', 'priceaverage': '8929', 'pricehigh': '9039'}, 'MPC85': {'comment': 'Large buyers', 'indicator': 'Flat', 'pricelow': '8598', 'priceaverage': '8929', 'pricehigh': '9039'}}}
我想解析嵌套结构,为此我想取产品名“Cheese”、“MPC70”、“MPI”、“MPC85”,将其作为“name”添加到内部dict中,并将其全部放入一个列表中。(分类(“奶酪”和“MPC”不再重要,并且将丢失)拥有这样的东西:
^{pr2}$到目前为止还不错,但当我在字典中查找“MPC”类别中的所有产品时,名称是“MPC85” 我的循环是这样的:
for item in products:
for subitem in products[item]:
products[item][subitem]['name'] = subitem
productlist.append(products[item][subitem])
#print products[item][subitem]
#print products[item][subitem]['name']
#print item + ' ' + subitem
print productlist
对于任何带注释的print语句,输出完全是我想要的,但是如果我打印整个列表,“MPC”产品的“name”键是“MPC85”\
经过一些尝试和错误,并确认@spectras循环实际起作用,我想如果我将dict赋给另一个变量
products2 = products
将循环改为循环products2
,而不是products
,整个过程正常。在
所以问题是:为什么python似乎在循环一个dict时有问题,而当我将dict赋给另一个变量时,它却如预期的那样做了?
编辑: 我做了什么,得到了什么:
In [3]: print products
{'Cheese': {'Cheese': {'comment': 'Markets quiet this week', 'indicator': 'Flat', 'pricelow': '3385', 'priceaverage': '3385', 'pricehigh': '3385'}}, 'MPC': {'MPC70': {'comment': 'Large buyers.High Ground.', 'indicator': 'Flat', 'pricelow': '8598', 'priceaverage': '8929', 'pricehigh': '9039'}, 'MPI:': {'comment': 'Large buyers.High Ground.', 'indicator': 'Flat', 'pricelow': '8598', 'priceaverage': '8929', 'pricehigh': '9039'}, 'MPC85': {'comment': 'Large buyers.High Ground.', 'indicator': 'Flat', 'pricelow': '8598', 'priceaverage': '8929', 'pricehigh': '9039'}}, 'Whey Powder': {'Whey Powder': {'comment': 'Dry Whey futures drop', 'indicator': 'Down', 'pricelow': '1124', 'priceaverage': '1124', 'pricehigh': '1124'}}, 'Casein': {'Casein': {'comment': 'No changes.', 'indicator': 'Down', 'pricelow': '7165', 'priceaverage': '7605', 'pricehigh': '8157'}}, 'Lactose': {'Lactose': {'comment': 'Lactose prices remain unchanged', 'indicator': 'Down', 'pricelow': '683', 'priceaverage': '683', 'pricehigh': '683'}}, 'Powders': {'NFDM': {'comment': 'Export volumes dropped.', 'indicator': 'Up', 'pricelow': '2408', 'priceaverage': '2408', 'pricehigh': '2408'}}, 'Caseinate': {'Caseinate': {'comment': 'actively selling.requested pricing.', 'indicator': 'Down', 'pricelow': '7716', 'priceaverage': '8598', 'pricehigh': '9479'}}, 'Cream': {'Butter': {'comment': 'Butter stocks increased', 'indicator': 'Down', 'pricelow': '3847', 'priceaverage': '3847', 'pricehigh': '3847'}}, 'WPC': {'WPC80': {'comment': 'WPC 80 \xe2\x80\x93 Supply continues.', 'indicator': 'Down', 'pricelow': '5300', 'priceaverage': '7165', 'pricehigh': '8267'}, 'IWPC80': {'comment': 'WPC 80 \xe2\x80\x93 Supply continues.', 'indicator': 'Down', 'pricelow': '5300', 'priceaverage': '7165', 'pricehigh': '8267'}}}
In [4]: %paste
for item in products:
for subitem in products[item]:
products[item][subitem]['name'] = subitem
#print products[item][subitem]
#print products[item][subitem]['name']
productlist.append(products[item][subitem])
#print item + ' ' + subitem
#print products[item][subitem]['name']
#print products[item]
#print products[item][subitem]
print productlist
## -- End pasted text --
[{'comment': 'Markets quiet this week', 'indicator': 'Flat', 'name': 'Cheese', 'pricelow': '3385', 'priceaverage': '3385', 'pricehigh': '3385'}, {'comment': 'Large buyers.High Ground.', 'indicator': 'Flat', 'name': 'MPC85', 'pricelow': '8598', 'priceaverage': '8929', 'pricehigh': '9039'}, {'comment': 'Large buyers.High Ground.', 'indicator': 'Flat', 'name': 'MPC85', 'pricelow': '8598', 'priceaverage': '8929', 'pricehigh': '9039'}, {'comment': 'Large buyers.High Ground.', 'indicator': 'Flat', 'name': 'MPC85', 'pricelow': '8598', 'priceaverage': '8929', 'pricehigh': '9039'}, {'comment': 'Dry Whey futures drop', 'indicator': 'Down', 'name': 'Whey Powder', 'pricelow': '1124', 'priceaverage': '1124', 'pricehigh': '1124'}, {'comment': 'No changes.', 'indicator': 'Down', 'name': 'Casein', 'pricelow': '7165', 'priceaverage': '7605', 'pricehigh': '8157'}, {'comment': 'Lactose prices remain unchanged', 'indicator': 'Down', 'name': 'Lactose', 'pricelow': '683', 'priceaverage': '683', 'pricehigh': '683'}, {'comment': 'Export volumes dropped.', 'indicator': 'Up', 'name': 'NFDM', 'pricelow': '2408', 'priceaverage': '2408', 'pricehigh': '2408'}, {'comment': 'actively selling.requested pricing.', 'indicator': 'Down', 'name': 'Caseinate', 'pricelow': '7716', 'priceaverage': '8598', 'pricehigh': '9479'}, {'comment': 'Butter stocks increased', 'indicator': 'Down', 'name': 'Butter', 'pricelow': '3847', 'priceaverage': '3847', 'pricehigh': '3847'}, {'comment': 'WPC 80 \xe2\x80\x93 Supply continues.', 'indicator': 'Down', 'name': 'IWPC80', 'pricelow': '5300', 'priceaverage': '7165', 'pricehigh': '8267'}, {'comment': 'WPC 80 \xe2\x80\x93 Supply continues.', 'indicator': 'Down', 'name': 'IWPC80', 'pricelow': '5300', 'priceaverage': '7165', 'pricehigh': '8267'}]
In [5]: type(products)
Out[5]: dict
In [6]: type(products['Cheese']
...: )
Out[6]: dict
编辑2: Ran建议从评论中截取,输出:
In [3]: print products
{'Cheese': {'Cheese': {'comment': 'Markets quiet this week', 'indicator': 'Flat', 'pricelow': '3385', 'priceaverage': '3385', 'pricehigh': '3385'}}, 'MPC': {'MPC70': {'comment': 'Large buyers.High Ground.', 'indicator': 'Flat', 'pricelow': '8598', 'priceaverage': '8929', 'pricehigh': '9039'}, 'MPI:': {'comment': 'Large buyers.High Ground.', 'indicator': 'Flat', 'pricelow': '8598', 'priceaverage': '8929', 'pricehigh': '9039'}, 'MPC85': {'comment': 'Large buyers.High Ground.', 'indicator': 'Flat', 'pricelow': '8598', 'priceaverage': '8929', 'pricehigh': '9039'}}, 'Whey Powder': {'Whey Powder': {'comment': 'Dry Whey futures drop', 'indicator': 'Down', 'pricelow': '1124', 'priceaverage': '1124', 'pricehigh': '1124'}}, 'Casein': {'Casein': {'comment': 'No changes.', 'indicator': 'Down', 'pricelow': '7165', 'priceaverage': '7605', 'pricehigh': '8157'}}, 'Lactose': {'Lactose': {'comment': 'Lactose prices remain unchanged', 'indicator': 'Down', 'pricelow': '683', 'priceaverage': '683', 'pricehigh': '683'}}, 'Powders': {'NFDM': {'comment': 'Export volumes dropped.', 'indicator': 'Up', 'pricelow': '2408', 'priceaverage': '2408', 'pricehigh': '2408'}}, 'Caseinate': {'Caseinate': {'comment': 'actively selling.requested pricing.', 'indicator': 'Down', 'pricelow': '7716', 'priceaverage': '8598', 'pricehigh': '9479'}}, 'Cream': {'Butter': {'comment': 'Butter stocks increased', 'indicator': 'Down', 'pricelow': '3847', 'priceaverage': '3847', 'pricehigh': '3847'}}, 'WPC': {'WPC80': {'comment': 'WPC 80 \xe2\x80\x93 Supply continues.', 'indicator': 'Down', 'pricelow': '5300', 'priceaverage': '7165', 'pricehigh': '8267'}, 'IWPC80': {'comment': 'WPC 80 \xe2\x80\x93 Supply continues.', 'indicator': 'Down', 'pricelow': '5300', 'priceaverage': '7165', 'pricehigh': '8267'}}}
In [4]: %paste
from pprint import pprint; from itertools import chain; pprint([(key, type(val).__name__, id(val)) for key, val in chain.from_iterable(x.items() for x in products.values())])
## -- End pasted text --
[('Cheese', 'dict', 64885352L),
('MPC70', 'dict', 64887800L),
('MPI:', 'dict', 64887800L),
('MPC85', 'dict', 64887800L),
('Whey Powder', 'dict', 65061480L),
('Casein', 'dict', 65061752L),
('Lactose', 'dict', 65062024L),
('NFDM', 'dict', 65062296L),
('Caseinate', 'dict', 65062568L),
('Butter', 'dict', 65063112L),
('WPC80', 'dict', 65062840L),
('IWPC80', 'dict', 65062840L)]
好吧,问题现在清楚了。在
关于我给你复制粘贴的样本线的说明:
这将遍历每个二级词典并打印:
因此,考虑到这些结果,有一点需要注意:
^{pr2}$→您的某些产品共享同一个dict。请参阅MPC70、MPI和MPC85如何具有相同的唯一标识符?在
结果,不是添加三个不同的dict,每个dict都添加了}。在
name
到产品列表中,而是最终添加了三次相同的dict,每次循环迭代都覆盖{这也解释了为什么复制粘贴改变了这个问题。当复制粘贴时,您创建了三个不同的dict,它们看起来正好相同。在
我们现在可以修复您的代码,因为我们知道必须显式地复制产品,而不是简单地重复使用它们:
另外,同样的循环写得更有效率:
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