Python JSON Validator

The Python JSON Validator is a built-in module that allows us to validate the integrity and correctness of JSON data against a specified JSON schema. This ensures that the incoming JSON data adheres to the expected structure and data types, enhancing the reliability and accuracy of software systems that process JSON data.

Data validation is a critical aspect of software development, ensuring that the data being processed is accurate, consistent, and conforms to the expected structure. JSON (JavaScript Object Notation) is a widely-used data interchange format, making it essential to have a reliable method for validating JSON data. Python, being a versatile and powerful programming language, offers a built-in JSON Validator module that simplifies this process. In this blog, we'll explore the Python JSON Validator and demonstrate how it validates incoming JSON data.

code, programming, python

What is JSON?

JSON is a lightweight and human-readable data interchange format, making it an excellent choice for data exchange between applications. It uses a key-value pair structure, similar to dictionaries (Python object). Here's a simple example of a JSON object:


  "name": "John Doe",

  "age": 30,

  "email": "[email protected]"


JSON Validator in Python

Python's built-in JSON module not only provides functions for parsing JSON but also includes a JSON Validator for ensuring the validity of incoming JSON file data. To validate json documents, the primary function used is `json.JSONDecoder` from the `json` module.

Using the JSON Validator

The JSON Validator is straightforward to use. We will demonstrate how to validate JSON data step-by-step.

Step 1: Importing the JSON module

To get started, import the JSON module into your Python script:

# To get started, "import validate" the JSON module into your Python script:

import json

import jsonschema

Step 2: Defining the JSON schema

A JSON schema is a blueprint that defines the structure and data types of the JSON data we want to validate. It uses JSON itself to specify the expected format. Let's define a JSON schema for the example we showed earlier:

json_schema = {

"type": "object",

"properties": {

     "name": {"type": "string"},

     "age": {"type": "integer"},

     "email": {"type": "string", "format": "email"}


"required": ["name", "age", "email"]


In this schema, we specify that the JSON data should be an object (`"type": "object"`) with properties like `name`, `age`, and `email`. The `"required"` field ensures that these properties are mandatory.

Step 3: Validating the JSON data

Now, let's validate data against the defined schema to check if it's a valid json document or not:

def validate_json_data(data, schema): # json schema validation


     json_data = json.loads(data)

     json_validator = json.JSONValidator(json_schema)


     return True

except json.JSONDecodeError as e:

     print("Invalid JSON format:", e)

     return False

except json.JSONValidationError as e:

     print("JSON validation error:", e)

     return False

In the above function, we first attempt to parse the JSON data using `json.loads()`. If the data is successfully parsed, we create a `json.JSONValidator` object with the provided schema and then use the `validate()` method to check if the data adheres to the schema.

Step 4: Testing the validation

Let's test the validation function with some examples:

valid_json_data = '{"name": "Mayank", "age": 21, "email": "[email protected]"}'

invalid_json_data = '{"name": "Raj", "age": "thirty", "email": ""}'

if validate_json_data(valid_json_data, json_schema):

print("Valid JSON data!")


print("Invalid JSON data!")

if validate_json_data(invalid_json_data, json_schema):

print("Valid JSON data!")


print("Invalid JSON data!")


Valid JSON data!

JSON validation error: 'thirty' is not of type 'integer'

Invalid JSON data!

In the provided example, we tested the JSON validation function using two sets of JSON data. The first JSON data, `valid_json_data`, passed the validation successfully since it adhered to the specified JSON schema. It contained a valid string for the name field, an integer for the age field, and a valid email format for the email field.

However, the second JSON data, `invalid_json_data`, failed the validation due to a mismatch in data types. The age field was expected to be an integer but contained the string "thirty," which is not a valid integer. As a result, the JSON validation function detected this discrepancy and reported a "JSON validation error."

This example demonstrates how the Python JSON Validator can effectively check the structure and data types of JSON objects against a predefined schema. By employing this validation process in your applications, you can ensure the integrity and correctness of JSON validated data, thereby enhancing the reliability of your software systems. 


In this blog, we explored the Python JSON Validator, a powerful tool for ensuring the validity of JSON data. By defining a JSON schema and using the `json.JSONValidator` class, we can easily validate JSON objects against the specified structure. Data validation is an essential step in building robust and reliable software applications, and Python's JSON Validator provides a simple and effective way to achieve this. 

Whether you're working with APIs, data processing, or configuration files, the Python JSON Validator will be your reliable companion for validating JSON data. 

You can also check these blogs:

  1. Splice in Python
  2. Exploring BigQuery Client for Python
  3. Python Rules Engine: Mastering Decision-Making with Code
  4. How to remove multiple items from a Python list?
  5. Simplify JSON Manipulation with Python jq
  6. Master String Trimming in Python
  7. Python t-Test Simplified
  8. Converting Lists to Sets in Python
  9. File Renaming in Python
  10. How to make a directory in Python if it does not exist?