Solving the Malformed Lambda Proxy Response Error in Python

Discover how to fix the `Malformed Lambda proxy response` error in AWS Lambda using Python by adjusting your code structure efficiently.
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Solving the Malformed Lambda Proxy Response Error in Python

When working with AWS Lambda and API Gateway, one of the most common issues developers encounter is the Malformed Lambda proxy response. This error can be frustrating, especially when it disrupts your application's functionality. In this guide, we will dive into the reasons behind this error and provide you with a detailed solution to overcome it.

Understanding the Issue

Specifically, you may see an error like this:

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

This error typically indicates that the response your Lambda function provides to API Gateway does not conform to the expected format. Let's take a closer look at a situation involving a Python-based Lambda function that takes user inputs and processes them.

The Scenario

Imagine you have a Lambda function developed in Python 3.6 that:

Accepts two numbers as input through an API Gateway GET method.

Processes these numbers to retrieve relevant data from a predefined list (in this case, List_r5).

Produces a JSON-formatted output containing a name, coordinates, and a message.

However, your Lambda function isn’t working as expected and keeps throwing the aforementioned error. This is likely due to how your code is structured.

The Solution

The primary issue at hand is that part of your code is incorrectly indented, leading to some statements being enclosed within a function that never gets called. Here’s how to resolve the issue:

Step-by-Step Fix

Identifying Code Structure: Look at the clo function definition and realize that the body of the response that should be processed is currently nested inside this function, hence never executed.

Adjusting Indentation:
To fix this, you need to un-indent the lines following the def clo(...) line so they are not considered part of the clo function. The corrected structure should look like this:

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

Key Highlights to Note

Return Function Object Correctly: Ensure that your Lambda function returns the correctly structured responseObject. This includes having defined status codes and correctly formatted headers.

Consistent Data Types: When you send data in the response, make sure it is in JSON format—which you've appropriately done here using json.dumps.

Test Your Changes: Always test your Lambda function after such modifications to ensure that it now correctly interacts with the API Gateway without generating errors.

Conclusion

Configuring AWS Lambda with API Gateway can sometimes lead to configurations errors, such as the Malformed Lambda proxy response. By ensuring that your code structure is correctly organized and adheres to AWS's required response format, you can easily resolve such issues. Remember to always check for proper indentation and the placement of your code blocks.

We hope this guide helps you troubleshoot and fix any issues with your AWS Lambda function. Happy coding!