TypeError: Object of type function is not JSON serializable

If you are a developer, then you know how frustrating it can be to encounter an error that prevents your code from running as expected. One such error that many developers encounter is the "TypeError: Object of type function is not JSON serializable."

In this guide, we will discuss what this error means, why it occurs, and steps you can take to fix it.

What is the "TypeError: Object of type function is not JSON serializable" error?

Simply put, the "TypeError: Object of type function is not JSON serializable" error is a Python error message that is thrown when JSON tries to serialize a Python function. Serialization is the process of converting data into a format that can be easily stored or transmitted over a network.

JSON (JavaScript Object Notation) is a lightweight data interchange format that is commonly used in web development. It is used to transmit data between a client and a server. However, it cannot serialize Python functions.

Why does the "TypeError: Object of type function is not JSON serializable" occur?

JSON can only serialize objects that are JSON serializable. A Python function is not JSON serializable, so attempting to serialize it using JSON results in the "TypeError: Object of type function is not JSON serializable" error.

How to Fix the "TypeError: Object of type function is not JSON serializable" Error

Now that we understand what the error is and why it occurs, let's discuss some steps you can take to fix it.

1. Remove the function from the code

The most straightforward way to fix this error is to remove the function from your code. If the function is not critical to your code's functionality, removing it could be the quickest and easiest solution.

2. Define a custom encoder

Another solution is to define a custom JSON encoder that can handle the serialization of Python functions. This can be done by subclassing the json.JSONEncoder class and overriding the default method.

import json

class CustomEncoder(json.JSONEncoder):
    def default(self, obj):
        if callable(obj):
            return obj.__name__
        return json.JSONEncoder.default(self, obj)

In this example, the default method checks if the object is callable, which means it is a function. If it is a function, the __name__ attribute of the function is returned. If it is not callable, the default JSONEncoder behavior is used.

You can then use this custom encoder when serializing your data.

data = {
    'name': 'John',
    'age': 30,
    'occupation': lambda: 'developer'
}

json.dumps(data, cls=CustomEncoder)

3. Convert the function to a string

Another solution is to convert the function to a string before serializing it using JSON. This can be done using the inspect module.

import inspect
import json

def my_function():
    return 'Hello, World!'

function_string = inspect.getsource(my_function)
data = {
    'name': 'John',
    'age': 30,
    'occupation': function_string
}

json.dumps(data)

In this example, the inspect.getsource function is used to get the source code of the function as a string before adding it to the data object that will be serialized.

4. Use a third-party library

Finally, you can use a third-party library that can serialize Python functions. One such library is dill.

import json
import dill

data = {
    'name': 'John',
    'age': 30,
    'occupation': lambda: 'developer'
}

json.dumps(data, default=dill.encode)

In this example, the dill.encode function is used as the default encoder for JSON.

Conclusion

In conclusion, the "TypeError: Object of type function is not JSON serializable" error is a common error that many Python developers encounter when working with JSON. However, by following the steps outlined in this guide, you can fix the error and avoid it in the future.