How Can I Make Custom Python Classes JSON Serializable?

Making Custom Python Classes JSON Serializable

When attempting to serialize custom Python classes to JSON using the json.dumps() function, an error may occur due to Python's default behavior of not natively supporting the serialization of custom objects.

Custom Serialization Method: .toJSON()

One approach to address this issue is to create a custom .toJSON() method within the class that implements the serialization logic. This method converts the object into a JSON-serializable dictionary by iterating over its attributes and generating a JSON string. Here's an example:

class FileItem:
    def __init__(self, fname):
        self.fname = fname

    def toJSON(self):
        return json.dumps({"filename": self.fname})

By calling the .toJSON() method, you can serialize the custom object to a JSON string:

x = FileItem('/foo/bar')
json_string = x.toJSON()

orjson Library

For a more comprehensive and efficient approach, it is recommended to use third-party libraries such as orjson. Orjson is a C extension for Python that provides blazing-fast JSON serialization and deserialization. With orjson, you can enable custom object serialization by defining a Metaclass:

import orjson

class JsonSerializableMeta(type):
    def __orjson__(cls):
        return cls.__dict__

class FileItem(metaclass=JsonSerializableMeta):
    def __init__(self, fname):
        self.fname = fname

This Metaclass overrides the __orjson__ method to return the object's attributes as a dictionary, enabling serialization to JSON.

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