How to add a key-value to JSON data retrieved from a file?

Question

I am new to Python and I am playing with JSON data. I would like to retrieve the JSON data from a file and add to that data a JSON key-value "on the fly".

That is, my json_file contains JSON data as-like the following:

{"key1": {"key1A": ["value1", "value2"], "key1B": {"key1B1": "value3"}}} 

I would like to add the "ADDED_KEY": "ADDED_VALUE" key-value part to the above data so to use the following JSON in my script:

{"ADDED_KEY": "ADDED_VALUE", "key1": {"key1A": ["value1", "value2"], "key1B": {"key1B1": "value3"}}} 

I am trying to write something as-like the following in order to accomplish the above:

import json  json_data = open(json_file) json_decoded = json.load(json_data)  # What I have to make here?!  json_data.close() 

Answer 1

Your json_decoded object is a Python dictionary; you can simply add your key to that, then re-encode and rewrite the file:

import json  with open(json_file) as json_file:     json_decoded = json.load(json_file)  json_decoded['ADDED_KEY'] = 'ADDED_VALUE'  with open(json_file, 'w') as json_file:     json.dump(json_decoded, json_file) 

I used the open file objects as context managers here (with the with statement) so Python automatically closes the file when done.