AWS Lambda - How to import a dependency from a Lambda Layer in python?

When working with AWS Lambda functions in Python, you might come across situations where you need to import external dependencies or libraries. AWS Lambda provides a feature called Lambda Layers that allows you to manage and share these dependencies across multiple functions. In this article, we will explore how to import a dependency from a Lambda Layer in Python.

What is a Lambda Layer?

AWS Lambda Layers are a distribution mechanism for libraries, custom runtimes, and other function dependencies. Layers let you manage your in-development function code independently from the unchanging code and resources that it uses.

Creating a Lambda Layer

The first step is to create a Lambda Layer that contains the dependency you want to import. Here's how you can create a Lambda Layer:

1. Create a new directory on your local machine and navigate to it.
2. Create a new directory inside the previous directory called python. This directory will contain the Python dependencies.
3. Install the required dependency using pip in the python directory. For example, if you want to import the requests library, run the following command:

This command installs the requests library inside the python directory.

4. Create an empty __init__.py file in the python directory. This file is required for Python to recognize the directory as a package.
5. Zip the contents of the python directory. You can do this by running the following command:

This command creates a zip file named mylayer.zip containing the python directory.

Uploading the Lambda Layer

Once you have created the Lambda Layer, you need to upload it to AWS Lambda. Here's how:

1. Sign in to the AWS Management Console and open the Lambda service.
2. Click on "Layers" in the left navigation pane.
3. Click on the "Create Layer" button.
4. Provide a name for your layer, such as "mylayer".
5. Upload the mylayer.zip file you created earlier.
6. Specify a compatible runtime. For example, if your Lambda function uses Python 3.8, choose "Python 3.8" as the runtime.
7. Click on the "Create" button to create the Lambda Layer.

Importing the Dependency in Your Lambda Function

Now that you have created the Lambda Layer, you can import the dependency in your Lambda function. Here's how:

1. Open your Lambda function in the AWS Management Console.
2. Scroll down to the "Layers" section.
3. Click on the "Add a layer" button.
4. In the "Choose a layer" dialog, select the Lambda Layer you created earlier.
5. Click on the "Add" button to add the layer to your Lambda function.
6. Save and deploy your Lambda function.

After adding the layer, you can import the dependency in your Python code using the standard import statement. For example, if you added a layer containing the requests library, you can import it like this:

Conclusion

Importing dependencies from a Lambda Layer in Python is a powerful feature provided by AWS Lambda. It allows you to manage and share common dependencies across multiple Lambda functions easily. By following the steps outlined in this article, you can import external libraries and dependencies into your Lambda functions without the need to include them in your deployment package.