Fixing the TypeError: Object of type coroutine is not JSON serializable in Azure Durable Functions

Learn how to fix the `TypeError: Object of type coroutine is not JSON serializable` error when working with Azure Durable Functions in Python, including code modifications and explanations.
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Introduction

When developing applications using Azure Durable Functions, particularly with Python, you may encounter various errors during execution. One such error is:

Microsoft.Azure.WebJobs.Script.Workers.Rpc.RpcException: Result: Failure Exception: TypeError: Object of type coroutine is not JSON serializable

This error can be frustrating, especially when you're attempting to implement an HTTP-triggered API. In this guide, we will explore what this error means, what causes it, and how you can effectively resolve it.

Understanding the Error

The error message indicates that the application is trying to convert a coroutine object into JSON format, which is not possible. This often happens when dealing with asynchronous function calls in Python.

What is a Coroutine?

In Python, coroutines are a way to define functions that can pause execution and yield control back to the event loop, which allows other functions to run. When you call an asynchronous function without awaiting it, it returns a coroutine object instead of the actual result.

The Cause of the Error

In your specific case, the error occurred in the following line of code:

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Solution Steps

To resolve the error, follow these steps to modify your code:

1. Await the Response Creation

When you call the create_check_status_response method, ensure that you precede it with the await keyword. This change allows the function to complete its execution and return the proper value, avoiding the TypeError. Here’s how you can modify your code:

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2. Review Other Asynchronous Calls

Ensure that any other functions that are asynchronous and return coroutine objects are also being awaited properly. This will help prevent similar issues in the future.

Conclusion

By following the suggested modifications above, you should be able to resolve the TypeError: Object of type coroutine is not JSON serializable error in your Azure Durable Functions application. Understanding how to properly handle asynchronous functions is crucial in Python development, especially when dealing with web applications and APIs.

If you encounter further challenges or questions, feel free to explore additional Azure documentation or consult community forums for more insights.