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The table:
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),
)
A category can have many children, but only 1 parent. I have got the list of dictionary values as follows using CTE: eg. For id :14, parent is 13 and traversed from parent 8->10->12->13->14 where parent 8 has no parent 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
]
}
]
I would like to get the attributes of the parent also embedded as subcategories in the list as:
{
"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.....
]
}
] Notice that 'path_info' has been deleted from the dictionary and each id has been displayed with its details. I want json dumps with the above indented format. How to go about? Using flask 0.10, python 2.7
427
To convert a Python List to JSON, use json. dumps() function. dumps() function takes list as argument and returns a JSON String.
Python possesses a default module, 'json,' with an in-built function named dumps() to convert the dictionary into a JSON object by importing the "json" module. "json" module makes it easy to parse the JSON strings which contain the JSON object.
You can save the Python dictionary into JSON files using a built-in module json. We need to use json. dump() method to do this. Use the indent parameter to prettyPrint your JSON data.
JSON FormatJSON at its top-level is a dictionary of attribute/value pairs, or key/value pairs as we've talked about dictionaries in this class. The values are numbers, strings, other dictionaries, and lists. Here is a simple example with just 4 attribute/value pairs.
There is a tolerable way to do this with a few list/dict comprehensions.
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)
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