Troubleshooting AWS Lambda: Fixing “No Module Named Lambda_Function” Error in Python

You’ve created your AWS Lambda function, zipped it, and uploaded it, expecting everything to work smoothly. But instead, you’re hit with the error: “Unable to import module ‘lambda_function’: No module named lambda_function.” Let’s walk through solving this issue to get your Lambda function running seamlessly.

Understanding the Error

This error typically stems from a mismatch between your Python file and the Lambda configuration setup. When deploying a Python Lambda function, AWS expects a specific file and function naming convention unless you specify otherwise.

Naming Conventions Matter

By default, AWS assumes your handler is named lambda_function.lambda_handler. This means you should:

1. File Name: Ensure your Python file is named lambda_function.py.
2. Function Name: Define a function within this file named lambda_handler.

Here’s a quick check you should perform:

• Verify File Name: Is your Python script named lambda_function.py?
• Check Function Signature: Does your script contain def lambda_handler(event, context):?

Adjust these to match if they don’t, and your error should be resolved.

Customizing the Handler

Sometimes, you might want more descriptive names for your files or functions. AWS Lambda allows you to customize the handler name to accommodate this. You can set a different handler in the Lambda function’s configuration:

1. Navigate to Your Lambda Function: In the AWS Management Console, go to your Lambda function.
2. Function Configuration: Look for the “Handler” setting.
3. Change Handler Setting: Modify this to match your file and function names, using the format filename.functionname.

For example, if your file is my_lambda.py and your function is my_handler, set the handler to my_lambda.my_handler.

For more on customizing handler names, check out the AWS Lambda Handler Documentation.

Proper Packaging of Dependencies

Another common pitfall when deploying Lambda functions is packaging dependencies. If your function uses external libraries, ensure they are included in your deployment package. Follow these steps:

1. Create a Folder: Organize your project files, including all dependencies installed using pip, inside a directory.
2. Activate Your Environment: Use virtualenv or a similar tool to manage dependencies and activate it before installing packages.
3. Install Dependencies Locally: Run pip install requests -t /path/to/your/project-dir. This will install any dependencies directly into your project folder.
4. Zip Contents: Compress the contents of your project directory, not the directory itself, into a single ZIP file. Upload this ZIP file to Lambda.

Staying updated on AWS’s practices and documentation can prevent common issues. Always ensure you’re following the latest guidelines provided by AWS.

Important Note on Python Usage: Always use the latest Python version supported by AWS Lambda — currently Python 3.12, for the most up-to-date features and security improvements.

Navigating these common issues can significantly streamline your AWS Lambda development process. Happy coding, and may your Lambda functions run error-free!