python - 重组字典

Question

我有一个 .csv 文件，我使用 csv.dictwriter 将它读入 python，看起来像这样：

[
    {'id':'1', 'date':'12312004','var1':'234', 'var2':'456'},
    {'id':'1', 'date':'12312005','var1':'200', 'var2':'466'},
    {'id':'1', 'date':'12312006','var1':'760', 'var2':'656'},
    {'id':'1', 'date':'12312007','var1':'215', 'var2':'256'},
    {'id':'2', 'date':'5312006','var1':'234', 'var2':'456'},
    {'id':'2', 'date':'5312007','var1':'200', 'var2':'466'},
    {'id':'2', 'date':'5312008','var1':'760', 'var2':'656'},
    {'id':'2', 'date':'5312009','var1':'215', 'var2':'256'},
]

我想将其重组为：

{'1': {
    '12312004': {'var1': '234', 'var2': '456'},
    '12312005': {'var1': '200', 'var2': '466'},
    '12312006': {'var1': '760', 'var2': '656'},
    '12312007': {'var1': '215', 'var2': '256'}},
 '2': {
     '5312006': {'var1': '234', 'var2': '456'},
     '5312007': {'var1': '200', 'var2': '466'},
     '5312008': {'var1': '760', 'var2': '656'},
     '5312009': {'var1': '215', 'var2': '256'}}
}

Answer 1

如果您的输入是一个列表，您可以这样做：

output = {}
for entry in input_list:
    entry = entry.copy()  # so we can mangle it
    id = entry.pop('id')
    date = entry.pop('date')
    output.setdefault(id, {})[date] = entry

该dict.setdefault()调用返回 key 的值id，但如果没有这样的 key，则第二个参数将添加到该outputkey 的字典中并返回。

演示：

>>> input_list = [
...     {'id':'1', 'date':'12312004','var1':'234', 'var2':'456'},
...     {'id':'1', 'date':'12312005','var1':'200', 'var2':'466'},
...     {'id':'1', 'date':'12312006','var1':'760', 'var2':'656'},
...     {'id':'1', 'date':'12312007','var1':'215', 'var2':'256'},
...     {'id':'2', 'date':'5312006','var1':'234', 'var2':'456'},
...     {'id':'2', 'date':'5312007','var1':'200', 'var2':'466'},
...     {'id':'2', 'date':'5312008','var1':'760', 'var2':'656'},
...     {'id':'2', 'date':'5312009','var1':'215', 'var2':'256'},
... ]
>>> output = {}
>>> for entry in input_list:
...     entry = entry.copy()  # so we can alter it
...     id = entry.pop('id')
...     date = entry.pop('date')
...     output.setdefault(id, {})[date] = entry
... 
>>> from pprint import pprint
>>> pprint(output)
{'1': {'12312004': {'var1': '234', 'var2': '456'},
       '12312005': {'var1': '200', 'var2': '466'},
       '12312006': {'var1': '760', 'var2': '656'},
       '12312007': {'var1': '215', 'var2': '256'}},
 '2': {'5312006': {'var1': '234', 'var2': '456'},
       '5312007': {'var1': '200', 'var2': '466'},
       '5312008': {'var1': '760', 'var2': '656'},
       '5312009': {'var1': '215', 'var2': '256'}}}