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pythonjsonappend
HappyPy
HappyPy

Reputation: 10697

append line to file and overwrite - python

How can I append a line to a json file and overwrite it with the same name?

data.json    
{
 'a': 1,
 'b': 2}

I tried

with open('data.json', 'r+') as json_file:
    data = json.load(json_file)
    data.update({'c': 3})
    json.dump(data,json_file)

but this appends all the data, not just the intended line

Upvotes: 0

Views: 131

Answers (1)

Max Voisard
Max Voisard

Reputation: 1942

First you need to read the JSON file and pass a second argument in the json.load() method, that being to preserve the order of the dictionary. So when assigning a key-value pair to the dictionary, OrderedDict will automatically append it to the end. Finally, write to the file.

import json
from collections import OrderedDict

with open('data.json', 'r') as json_file:
    data = json.load(json_file, object_pairs_hook=OrderedDict)
    data['c'] = 3

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

Upvotes: 2

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