How I can create Python class from JSON object?

Creating Python classes from JSON objects can be accomplished using the python-jsonschema-objects library, which is built on top of jsonschema. This library provides automatic class-based binding to JSON schemas for use in Python.

Installing the Required Library

First, install the python-jsonschema-objects library ?

pip install python-jsonschema-objects

Defining a JSON Schema

Let's start with a sample JSON schema that defines the structure of a Person object ?

schema = '''{
    "title": "Example Schema",
    "type": "object",
    "properties": {
        "firstName": {
            "type": "string"
        },
        "lastName": {
            "type": "string"
        },
        "age": {
            "description": "Age in years",
            "type": "integer",
            "minimum": 0
        },
        "dogs": {
            "type": "array",
            "items": {"type": "string"},
            "maxItems": 4
        },
        "gender": {
            "type": "string",
            "enum": ["male", "female"]
        },
        "deceased": {
            "enum": ["yes", "no", 1, 0, "true", "false"]
        }
    },
    "required": ["firstName", "lastName"]
}'''

print("Schema defined successfully")

Schema defined successfully

Converting Schema to Python Class

Now we can convert the JSON schema into a Python class using the ObjectBuilder ?

import python_jsonschema_objects as pjs

# Build the class from schema
builder = pjs.ObjectBuilder(schema)
ns = builder.build_classes()

# Get the generated class
Person = ns.ExampleSchema

# Create an instance
jack = Person(firstName="Jack", lastName="Sparrow")

print(f"Name: {jack.firstName} {jack.lastName}")
print(f"Age: {jack.age}")

Working with Class Instances

The generated class behaves like a regular Python class with additional validation ?

# Setting valid properties
jack.age = 30
jack.gender = "male"
jack.dogs = ["Buddy", "Max"]

print(f"Updated Person: {jack.firstName} {jack.lastName}, Age: {jack.age}")
print(f"Gender: {jack.gender}")
print(f"Dogs: {jack.dogs}")

Schema Validation

The library automatically validates data against the schema constraints ?

# This will raise a validation error
try:
    jack.age = -2  # Violates minimum: 0 constraint
except Exception as e:
    print(f"Validation Error: {e}")

# This will also raise an error
try:
    jack.gender = "other"  # Not in enum values
except Exception as e:
    print(f"Validation Error: {e}")

Key Benefits

Alternative Approach Using dataclasses

For simpler cases, you can also use Python's built-in dataclasses ?

import json
from dataclasses import dataclass
from typing import List, Optional

@dataclass
class Person:
    firstName: str
    lastName: str
    age: Optional[int] = None
    dogs: Optional[List[str]] = None
    gender: Optional[str] = None

# Create from JSON
json_data = '{"firstName": "John", "lastName": "Doe", "age": 25}'
person_dict = json.loads(json_data)
person = Person(**person_dict)

print(f"Person: {person.firstName} {person.lastName}, Age: {person.age}")

Person: John Doe, Age: 25

Conclusion

The python-jsonschema-objects library provides powerful automatic validation and class generation from JSON schemas. For simpler use cases, Python's built-in dataclasses offer a lightweight alternative for creating classes from JSON data.