Python | Check whether a string is valid json or not

Given a Python String, the task is to check whether the String is a valid JSON object or not. Let’s try to understand the problem using different examples in Python.

Validate JSON String in Python

There are various methods to Validate JSON schema in Python here we explain some generally used methods for validating JSON schema in Python which are the following:

• Check Whether a String Is Valid JSON
• Use JSON Schema to Validate JSON Strings
• Checking Validity for Multi-Line JSON String

Check Whether a String Is Valid JSON

In the below example, the string is an invalid JSON because, the string characters are enclosed in single quotes (‘), but as per valid JSON schema, strings must be enclosed in double quotes (“).

Python3

# Python code to demonstrate
# checking whether string
# is valid json or not

import json

ini_string = "{'akshat' : 1, 'nikhil' : 2}"

# printing initial ini_string
print ("initial string", ini_string)

# checking for string
try:
    json_object = json.loads(ini_string)
    print ("Is valid json? true")
except ValueError as e:
    print ("Is valid json? false")

Output:

initial string {'akshat' : 1, 'nikhil' : 2}
Is valid json? false

Use JSON Schema to Validate JSON Strings

In this example the below code uses a function, `is_valid`, to check JSON string validity with `json.loads()`. It tests the function on three JSON strings containing various data types and prints whether each string is valid or not.

Python3

import json


# function to check for JSON String validity
def is_valid(json_string):
    print("JSON String:", json_string)
    try:
        json.loads(json_string)
        print("  Is valid?: True")
    except ValueError:
        print("  Is valid?: False")
        return None


# checking for string and integers
is_valid('{"name":"John", "age":31, "Salary":2500000}')
# checking for integer and float
is_valid('{ "Subjects": {"Maths":85.01, "Physics":90}}')
# checking for boolean type values
is_valid('{"success": true}')

Output:

JSON String: {"name":"John", "age":31, "Salary":2500000}
  Is valid?: True
JSON String: { "Subjects": {"Maths":85.01, "Physics":90}}
  Is valid?: True
JSON String: {"success": true}
  Is valid?: True

Checking Validity for Multi-Line JSON String

Here we have taken a sample, multi-line Python string, and we’ll try to check the validity of the String for a valid JSON string or not. Although this String contains multiple line-breaks, still json.JSONDecoder able to parse this String.

Python3

import json


# function to check for JSON String validity
def is_valid(json_string):
    print("JSON String:", json_string)
    try:
        json.loads(json_string)
        print("  Is valid?: True")
    except ValueError:
        print("  Is valid?: False")
        return None


# parsing multi-line JSON string
json_str = """
{
    "Person": [
        {"name": "P_1", "age": 42},
        {"name": "P_2", "age": 21},
        {"name": "P_3", "age": 36}
    ],
    "location": "1.1.0",
    "Country": "IND"
}
"""
# call function for validation check
# of the Python String
is_valid(json_str)

Output:

JSON String: 
{
    "Person": [
        {"name": "P_1", "age": 42},
        {"name": "P_2", "age": 21},
        {"name": "P_3", "age": 36}
    ],
    "location": "1.1.0",
    "Country": "IND"
}
  Is valid?: True