How to Iterate through nested JSON in Python

Question

I would like to find out how I can iterate through the Following JSON in Python 3 Specifically I would like to be able to pull out 'id' and 'lname'. My actual JSON file has about 300 entries

{
"datainfos": [{
        "DataInfo": [{
            "id": 1,
            "lname": "Altitude",
            "max": 62.79999923706055,
            "min": -37.20000076293945,
            "numInstances": 1,
            "sname": "ALT",
            "unit": "m"
        }]
    },
    {
        "DataInfo": []
    },
    {
        "DataInfo": [{
            "id": 3,
            "lname": "Position Error",
            "max": 0,
            "min": 0,
            "numInstances": 1,
            "sname": "EPE",
            "unit": "m"
        }]
    },
    {
        "DataInfo": [{
            "id": 4,
            "lname": "HDOP",
            "max": 0,
            "min": 0,
            "numInstances": 1,
            "sname": "HDOP",
            "unit": ""
        }]
    }
]
}

My code is as below:

import json

f = open('data1.json')
data = json.load(f)
f.close()


for dataitems in data['datainfos']:
    print (dataitems['DataInfo'])

Python returns a list, not a dictionary. When I try to use the following code

import json

f = open('data1.json')
data = json.load(f)
f.close()


for dataitems in data['datainfos']:
    print (dataitems['DataInfo']['lnames'])

I get the error:

Traceback (most recent call last): File "C:\\Users\\phil\\Documents\\Python Scripts\\UMP-VDR\\Testing Files\\convertjson.py", line 9, in print (dataitems['DataInfo']['lnames']) TypeError: list indices must be integers or slices, not str [Finished in 0.1s]

Answer 1

Use this code because your DataInfo is array.

import json

f = open('data1.json')
data = json.load(f)
f.close()

for dataitems in data['datainfos']:
    for datainfo in dataitems['DataInfo']:
        print(datainfo['id'], datainfo['lname'])

Or change your json file like this:

{
    "datainfos": [
        {
            "DataInfo":
                {
                    "id": 1,
                    "lname": "Altitude",
                    "max": 62.79999923706055,
                    "min": -37.20000076293945,
                    "numInstances": 1,
                    "sname": "ALT",
                    "unit": "m"
                }
        },
        {
            "DataInfo": {}
        },
        {
            "DataInfo": 
                {
                    "id": 3,
                    "lname": "Position Error",
                    "max": 0,
                    "min": 0,
                    "numInstances": 1,
                    "sname": "EPE",
                    "unit": "m"
                }

        },
        {
            "DataInfo": 
                {
                    "id": 4,
                    "lname": "HDOP",
                    "max": 0,
                    "min": 0,
                    "numInstances": 1,
                    "sname": "HDOP",
                    "unit": ""
                }

        }
    ]
}

And change your code like this:

import json

f = open('asd.json')
data = json.load(f)
f.close()

for dataitems in data['datainfos']:
    if(dataitems['DataInfo']):
        print(dataitems['DataInfo']['id'], dataitems['DataInfo']['lname'])

Answer 2

Iterating over a dictionary in python will return the keys by default. You probably want .items() . But in this case you probably want:

import json
data = json.load(open('file.json'))
out = []
for x in data['datainfos']:
    if x['DataInfo']:
        out.append((x['DataInfo'][0]['id'], x['DataInfo'][0]['lname']))
print(out)

>>> [(1, 'Altitude'), (3, 'Position Error'), (4, 'HDOP')]

Answer 3

Whatever i understand from your question is that you want id and lname for that particular id. So to do that in simple way with n^2 complexity is as below:

import json
f = open('data.json')
data = json.load(f)
f.close()
for dataitems in data['datainfos']:
    for DataInfo in dataitems['DataInfo']:
        print(DataInfo['id'],DataInfo['lname'])

This will give you the particular id with lname. And if you want to store it somewhere then add us to that variable.

Answer 4

for x in range(0,len(sample_dict.get('datainfos'))):

    if len(sample_dict.get('datainfos')[x]['DataInfo'])==0:
        print('Empty list')

    else:
        print('ID IS {}, NAME IS {}'.format(sample_dict.get('datainfos')[x]['DataInfo'][0]['id'],sample_dict.get('datainfos')[x]['DataInfo'][0]['lname']))

This will iterate and print id and names. Will print empty for no name & ID. Your json is stored as sample_dict