Python JSON add Key-Value pair

Question

I'm trying to add key value pairs into the existing JSON file. I am able to concatenate to the parent label, How to add value to the child items?

JSON file:

{
  "students": [
    {
      "name": "Hendrick"
    },
    {
      "name": "Mikey"
    }
  ]
}

Code:

import json

with open("input.json") as json_file:
    json_decoded = json.load(json_file)

json_decoded['country'] = 'UK'

with open("output.json", 'w') as json_file:
    for d in json_decoded[students]:
        json.dump(json_decoded, json_file)

Expected Results:

{
  "students": [
    {
      "name": "Hendrick",
      "country": "UK"
    },
    {
      "name": "Mikey",
      "country": "UK"
    }
  ]
}

user2390182 · Accepted Answer · 2018-10-29 10:16:19Z

5

You can do the following in order to manipulate the dict the way you want:

for s in json_decoded['students']:
    s['country'] = 'UK'

json_decoded['students'] is a list of dictionaries that you can simply iterate and update in a loop. Now you can dump the entire object:

with open("output.json", 'w') as json_file:
    json.dump(json_decoded, json_file)

answered Oct 29, 2018 at 10:16

user2390182

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Comments

Roopak A Nelliat · Accepted Answer · 2018-10-29 11:11:42Z

2

import json

with open("input.json", 'r') as json_file:
    json_decoded = json.load(json_file)

    for element in json_decoded['students']:
        element['country'] = 'UK'

    with open("output.json", 'w') as json_out_file:
        json.dump(json_decoded, json_out_file)

opened a json file i.e. input.json
iterated through each of its element
add a key named "country" and dynamic value "UK", to each element
opened a new json file with the modified JSON.

Edit:

Moved writing to output file inside to first with segment. Issue with earlier implemenation is that json_decoded will not be instantiated if opening of input.json fails. And hence, writing to output will raise an exception - NameError: name 'json_decoded' is not defined

edited Oct 29, 2018 at 11:11

Roopak A Nelliat

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answered Oct 29, 2018 at 10:30

Talha Ghaffar

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Comments

Rohit-Pandey · Accepted Answer · 2018-10-29 10:29:39Z

0

This gives [None, None] but update the dict:

a = {'students': [{'name': 'Hendrick'}, {'name': 'Mikey'}]}
[i.update({'country':'UK'}) for i in a['students']]
print(a)

answered Oct 29, 2018 at 10:29

Rohit-Pandey

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