Serialize and Deserialize complex JSON in Python

JSON stands for JavaScript Object Notation. It is a format that encodes the data in string format. JSON is language-independent and because of that, it is used for storing or transferring data in files. 

Serialization of JSON object: It means converting a Python object (typically a dictionary) into a JSON formatting string.

Deserialization of JSON object: It is just the opposite of serialization, meaning converting a JSON-formatted string back to a Python Object.

JSON Object is defined using curly braces{} and consists of a key-value pair. It is important to note that the JSON object key is a string and its value can be any primitive(e.g. int, string, null) or complex data type (e.g. array).

Example of JSON Object:

{
 "id":101,
 "company" : "GeeksForGeeks"
}

Complex JSON objects are those objects that contain a nested object inside the other. Example of Complex JSON Object.

{
 "id":101,
 "company" : "GeeksForGeeks",
 "Topics" : { "Data Structure",
              "Algorithm",
              "Gate Topics" }
}

Serialization and Deserialization of JSON Object

Python and the JSON module work exceptionally well with dictionaries. For serializing and deserializing JSON objects in Python, you can utilize the “__dict__ “attribute available on many Python objects. 

This attribute is a dictionary used to store an object’s writable attributes. You can leverage this attribute effectively when working with JSON data, making the process seamless and efficient.

Code:

Python3

import json
class GFG_User(object):
    def __init__(self, first_name: str, last_name: str):
        self.first_name = first_name
        self.last_name = last_name

user = GFG_User(first_name="Jake", last_name="Doyle")
json_data = json.dumps(user.__dict__)
print(json_data)
print(GFG_User(**json.loads(json_data)))

Output: 

{"first_name": "Jake", "last_name": "Doyle"} 
__main__.GFG_User object at 0x105ca7278

Note: The double asterisks ** in the GFG_User(**json.load(json_data) line may look confusing. But all it does is expand the dictionary.

Serialization and Deserialization of Complex JSON Objects

Now things get tricky while dealing with complex JSON objects as our trick “__dict__” doesn’t work anymore.

Code: 

Python3

from typing import List
import json


class Student(object):
    def __init__(self, first_name: str, last_name: str):
        self.first_name = first_name
        self.last_name = last_name


class Team(object):
    def __init__(self, students: List[Student]):
        self.students = students


student1 = Student(first_name="Geeky", last_name="Guy")
student2 = Student(first_name="GFG", last_name="Rocks")
team = Team(students=[student1, student2])
json_data = json.dumps(team.__dict__, indent=4)
print(json_data)

Output: 

TypeError: Object of type Student is not JSON serializable

But if you look at the documentation of the dump function you will see there is a default setting that we can use. Simply by replacing the line:

json_data = json.dumps(team.__dict__, indent=4)

to this line:

json_data = json.dumps(team.__dict__, default=lambda o: o.__dict__, indent=4)

And everything works now as before. Now, let’s look at code of serializing and deserializing complex object:

Code: 

The code defines two classes, Student and Team. The serialization process converts the team object into a JSON string, using a lambda function to transform the objects into dictionaries for JSON compatibility and then deserializes them back into Python objects.

Python3

from typing import List
import json

class Student(object):
    def __init__(self, first_name: str, last_name: str):
        self.first_name = first_name
        self.last_name = last_name

class Team(object):
    def __init__(self, students: List[Student]):
        self.students = students

student1 = Student(first_name="Geeky", last_name="Guy")
student2 = Student(first_name="GFG", last_name="Rocks")
team = Team(students=[student1, student2])

# Serialization
json_data = json.dumps(team, default=lambda o: o.__dict__, indent=4)
print(json_data)

# Deserialization
decoded_team = Team(**json.loads(json_data))
print(decoded_team)

Output: 

{
    "students": [
        {
            "first_name": "Geeky",
            "last_name": "Guy"
        },
        {
            "first_name": "GFG",
            "last_name": "Rocks"
        }
    ]
}
__main__.Team object at 0x105cd41d0

We have explained how to serialize and deserialize complex JSON objects in Python in easy words. This is a step-by-step tutorial to properly demonstrate the programs on how to serialize complex JSON and how to deserialize complex JSON.