熊猫-按3栏向JSON输出组

Question

我有关于汽车的carsML数据：

+-------+-------------+--------------------+
| Manuf |    Model    |        Type        |
+-------+-------------+--------------------+
| VW    | VWModel 1   | VWModel 1 Type 1   |
| VW    | VWModel 2   | VWModel 2 Type 1   |
| VW    | VWModel 2   | VWModel 2 Type 2   |
| Opel  | OpelModel 1 | OpelModel 1 Type 1 |
| Opel  | OpelModel 2 | OpelModel 2 Type 1 |
| Opel  | OpelModel 2 | OpelModel 2 Type 2 |
+-------+-------------+--------------------+

我需要将唯一的值导出到JSON。我知道如何达到2级：

j = carsML.groupby('Manuf ')['Model'].unique().to_json()

这为Manufacturers和Models提供了很好的JSON，但我不知道如何在第3层(Types)上扩展它。

最后的JSON应该如下所示：

{"Opel":
{"OpelModel 1": ["OpelModel 1 Type 1"]},
["OpelModel 2":["OpelModel 2 Type 1","OpelModel 2 Type 1"]],
"VW":
{"VWModel 1":["VWModel 1 Type 1"]},
{"VWModel 2":["VWModel 2 Type 1","VWModel 2 Type 2"]}}

Answer 1

首先通过按2列分组创建MultiIndex Series，然后在字典理解嵌套字典中创建：

s = carsML.groupby(['Manuf','Model'])['Type'].unique().apply(list)
d = {l: s.xs(l).to_dict() for l in s.index.levels[0]}

对于json，使用嵌套字典中的json.dumps：

import json
j = json.dumps({l: s.xs(l).to_dict() for l in s.index.levels[0]})

print (j)
{"Opel": {"OpelModel 1": ["OpelModel 1 Type 1"], 
          "OpelModel 2": ["OpelModel 2 Type 1", "OpelModel 2 Type 2"]},
 "VW": {"VWModel 1": ["VWModel 1 Type 1"], 
        "VWModel 2": ["VWModel 2 Type 1", "VWModel 2 Type 2"]}}