string is a JSON object or JSON array in Python?

Question

I am reading JSON file line by line. Few lines contain JSON objects while other contains JSON array. I am using json.loads(line) function to get JSON from each line.

def read_json_file(file_name):
    json_file = []
    with open(file_name) as f:
        for line in f:
            json_file.append((line))

    json_array = []
    for obj in json_file:
        try:
            json_array.append(json.loads(obj))
        except ValueError:
            print("data was not valid JSON")

    return json_array

Is there any way that I can find out that object I am reading is JSON Object or JSON array? I want to save all the result in json_array.

I will be thankful to you if anyone can help me.

Why are you reading it line by line? Is that a file with many JSONs separated by newline? — zvone
– zvone, Commented Oct 15, 2016 at 9:05
@zvone yes some lines have simple JSON object while others have JSON array. But these JSON array object are also placed line by line — Ayaz Ahmad Tarar
– Ayaz Ahmad Tarar, Commented Oct 15, 2016 at 9:09

ManuelSchneid3r · Accepted Answer · 2017-12-06 15:28:56Z

7

In python, JSON object is converted into dict and JSON list is converted into list datatypes.

So, if you want to check the line content which should be valid JSON, is JSON Object or JSON Array, then this code will helps you:-

import json

# assume that, each line is valid json data
obj = json.loads(line)

# if returns true, then JSON Array
isinstance(obj, list)

# if returns true, then JSON Object.
isinstance(obj, dict)

edited Dec 6, 2017 at 15:28

ManuelSchneid3r

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answered Oct 15, 2016 at 9:35

Akshay Pratap Singh

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1 Comment

Ayaz Ahmad Tarar Over a year ago

My problem was solved using isintance(). Thank u so much

volcano · Accepted Answer · 2016-10-15 09:25:14Z

0

The problem with your code - if line does not contain full JSON object - it seldom does - it will nearly always fail.

Unlike in Java, in Python JSON is naturally represented by hierarchical mixture of list and dictionary elements. So, if you are looking for list elements in your JSON, you may use recursive search.

If you want to check if your file is valid JSON - the code below is simpler and shorter test

try:
    with open(file_name) as f:
        json_obj = json.load(f)
    except:
        print "Not valid JSON"

EDIT Is it JSON file or JSON schema?

In the latter, you may just check if your object is list

obj = json.loads(line)
isintance(obj, list)

As I have already stated, there's no such thing as "JSON object" in Python

PS If you read file line by line, and each line is JSON object - it's not a JSON file, it's a file where each string contains JSON. Otherwise, your test will fail on the first line already, which will be just

edited Oct 15, 2016 at 9:25

answered Oct 15, 2016 at 9:05

volcano

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1 Comment

Ayaz Ahmad Tarar Over a year ago

Line contains complete json object. But few other lines contains JSON array. I know how to check validity. How to check the object I have read is JSON object or JSON array?

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