从python中的字典列表创建分层json转储

Question

桌子:

categories = Table("categories", metadata,
                   Column("id", Integer, primary_key=True),
                   Column("name", String),
                   Column("parent_id", Integer, ForeignKey("categories.id"),
                          CheckConstraint('id!=parent_id'), nullable=True),

)

一个类别可以有很多孩子,但只有一个孩子.我使用CTE得到了如下字典值列表:例如.对于id:14,parent是13并且从父8-> 10-> 12-> 13-> 14遍历,其中父8没有父id.

[
    {
      "id": 14, 
      "name": "cat14", 
      "parent_id": 13, 
      "path_info": [
        8, 
        10, 
        12, 
        13, 
        14
      ]
    }, 
    {
      "id": 15, 
      "name": "cat15", 
      "parent_id": 13, 
      "path_info": [
        8, 
        10, 
        12, 
        13, 
        15
      ]
    }
  ]

我想将父类的属性也嵌入到列表中作为子类别:

{
  "id": 14, 
  "name": "cat14", 
  "parent_id": 13, 
  "subcats": [
       {
         "id: 8", 
         "name": "cat8", 
         "parent_id":null
       }, 
       {
         "id: 10", 
         "name": "cat10", 
         "parent_id":8
       },  
       {
         "id: 12", 
         "name": "cat12", 
         "parent_id":10
       },   
      and similarly for ids 13 and 14..... 
     ]
}, 
{
  "id": 15, 
  "name": "cat15", 
  "parent_id": 13, 
  "subcats": [
       {
         "id: 8", 
         "name": "cat8", 
         "parent_id":null
       }, 
       {
         "id: 10", 
         "name": "cat10", 
         "parent_id":8
       },  
       {
         "id: 12", 
         "name": "cat12", 
         "parent_id":10
       },   
       and similarly for ids 13, 14, 15..... 
     ]
}

请注意,'path_info'已从字典中删除,并且每个id都已显示其详细信息.我想要以上面缩进格式的json转储.怎么去？使用烧瓶0.10,python 2.7

Answer 1

有一种可以接受的方法可以通过一些列表/字典理解来做到这一点。

lst = [{"id": 14, "name": "cat14", "parent_id": 13, "path_info": [8, 10, 12, 13, 14]}, {"id": 15, "name": "cat15", "parent_id": 13, "path_info": [8, 10, 12, 13, 15]}]

master_dct = { d['id'] : d for d in lst}
for d in lst:
    d['subcats'] = [{field : master_dct[i][field] for field in ['id', 'name', 'parent_id']} \
        for i in d['path_info'] if i in master_dct]

import json
with open('out.json', 'w') as f:
    json.dump(lst, f)