How to append in a json file in Python?

Question

I have the a json file whose contents is {"67790": {"1": {"kwh": 319.4}}}. Now I create a dictionary a_dict which I need to append it into the json file. I tried the following but was not able to do it correctly. Where I'm going wrong?

with open(DATA_FILENAME, 'a') as f:
   json_obj = json.dump(a_dict, json.load(f)
   f.write(json_obj)
   f.close()

question from:https://stackoverflow.com/questions/18980039/how-to-append-in-a-json-file-in-python

Answer 1

Assuming you have a test.json file with the following content:

{"67790": {"1": {"kwh": 319.4}}}

Then, the code below will load the json file, update the data inside using dict.update() and dump into the test.json file:

import json

a_dict = {'new_key': 'new_value'}

with open('test.json') as f:
    data = json.load(f)

data.update(a_dict)

with open('test.json', 'w') as f:
    json.dump(data, f)

Then, in test.json, you'll have:

{"new_key": "new_value", "67790": {"1": {"kwh": 319.4}}}

Hope this is what you wanted.