Resolving the TypeError: Object of type ndarray is not JSON serializable in Python APIs

Learn how to fix the common serialization error in Python when returning numpy arrays from an API endpoint. Ensure your API works smoothly with JSON data.
---

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Object of type ndarray is not JSON serializable: API endpoint

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Resolving the TypeError: Object of type ndarray is not JSON serializable in Python APIs

When developing a Python script that interacts with a web API, encountering errors can often feel overwhelming, especially if you're not entirely sure what went wrong. One such error that many developers face is the TypeError: Object of type ndarray is not JSON serializable. In this guide, we'll unravel this issue, understand why it happens, and explore how to resolve it effectively.

The Problem

You created a Python script that successfully processes input data and interacts with a machine learning model to produce predictions. However, when deploying your script to a REST API endpoint and testing it, you encountered the following error:

[[See Video to Reveal this Text or Code Snippet]]

This error can be confusing, especially when your input appears to be a straightforward Python list, rather than a numpy array. So, what could be causing this issue?

Understanding the Core Issue

Why Cannot ndarray be Serialized?

JSON Serialization: JSON (JavaScript Object Notation) is a text format that can represent structured data. It does not natively understand numpy types, which are specialized objects in Python designed for efficient numerical computations.

Numpy Arrays: Numpy arrays are not standard Python objects. As a result, they cannot be directly converted into JSON, leading to serialization errors when your API attempts to return the prediction.

The Solution

The solution to this problem is straightforward: convert the numpy array into a format that is JSON serializable before returning it. Specifically, you should convert the numpy array to a Python list using the .tolist() method.

Here’s How to Fix It

Modify your run function to include a conversion step before returning the prediction. Here's the recommended change:

[[See Video to Reveal this Text or Code Snippet]]

Step-by-Step Explanation:

Call predict(): Continue using your model's predict() function to generate predictions.

Convert to List: Add .tolist() after the prediction line to convert the ndarray to a list.

Return the Value: Finally, return this list from your API. This list can now be serialized into JSON without any issues.

Conclusion

By following these simple steps, you can effectively resolve the TypeError: Object of type ndarray is not JSON serializable error in your Python API. This change not only ensures that your output is compatible with JSON serialization but also enhances the robustness of your API by gracefully handling unforeseen errors.

If you have encountered this issue in your projects, I hope this guide has helped clarify the problem and provided you with a clear path to a solution. Happy coding!