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Anurag Rana
Anurag Rana

Posted on • Originally published at pythoncircle.com on

Python Script to Validate, format and Beautify JSON string

As per official JSON website, JSON is a light-weight data interchange format. It is easy for humans to read and write. It is easy for machines to parse and generate. It is based on a subset of the JavaScript Programming Language, Standard ECMA-262 3rd Edition — December 1999.

In this small article we will see how to validate and format the JSON string using python.

Format JSON string:

import json

json_string = '{"first_name": "Anurag", "last_name":"Rana", "key3": {"key1":"key2"}}'

try:
    parsed_json = json.loads(json_string)
    print(json.dumps(parsed_json, indent = 4,sort_keys=False))
except Exception as e:
    print(repr(e))

output:

rana@Brahma: scripts$ python3 jsonParse.py 
{
    "first_name": "Anurag",
    "last_name": "Rana",
    "key3": {
       "key1": "key2"
    }
}
rana@Brahma: scripts$

Parameter indent decides the number of spaces to use for indentation. Parameter sort_keys decides whether the keys in formatted JSON should be in sorted order or not. The default value is False.

Format JSON file:

We can use the same code to format and validate the JSON file. Place a .json file with below content in the current working directory.

{"a": "b","c": "d","e": ["f","g","h"]}

Now use this piece of code to format the json file.

import json

json_string = None

with open("json_file.json") as f:
    json_string = f.read()
try:
    parsed_json = json.loads(json_string)
    formatted_json = json.dumps(parsed_json, indent = 4,sort_keys=True)
    with open("json_file.json","w") as f:
    f.write(formatted_json)
except Exception as e:
    print(repr(e))

Error in JSON validation:

Any error in JSON string will be reported with exact location in string.

For example, a comma is missing in below JSON string.

import json

json_string = '{"first_name": "Anurag" "last_name":"Rana", "key3": {"key1":"key2"}}'

try:
    parsed_json = json.loads(json_string)
    print(json.dumps(parsed_json, indent = 4,sort_keys=True))
except Exception as e:
    print(repr(e))

output:

JSONDecodeError("Expecting ',' delimiter: line 1 column 25 (char 24)",)

Bonus:

You can pretty-print the small JSON string directly at command terminal without using python script file. Use below line of code.

echo '{"first_name": "Anurag", "last_name": "rana"}' | python -m json.tool

output:

{
 "first_name": "Anurag",
 "last_name": "rana"
}

You can add this crome app to your browser to validate and beautify the JSON strings.

Originally published at www.pythoncircle.com.

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