When running an AWS Lambda function that imports rpy2.robjects, the following error occurs:
ModuleNotFoundError: No module named '_cffi_backend'
This error is caused by the missing _cffi_backend module, which is part of the cffi library. The issue typically arises because AWS Lambda uses Amazon Linux as its runtime environment, and cffi (a dependency of rpy2) includes compiled components that must match the Lambda runtime environment. If the package is installed on a different OS (e.g., macOS or Windows), it won’t work on Lambda.
You need to package your Lambda function with rpy2 and its dependencies in an Amazon Linux environment. Here are two approaches:
Option 1: Use a Lambda Layer A Lambda Layer allows you to bundle dependencies separately and reuse them across multiple functions.
Create a Directory for Dependencies: mkdir lambda-layer && cd lambda-layer mkdir python
Set Up Amazon Linux Environment: Use Docker to mimic the AWS Lambda runtime: docker run -it --rm -v $(pwd):/lambda amazonlinux:2 /bin/bash
Install Required Packages in Docker: Inside the Docker container:
yum update -y yum install -y python3-pip python3-devel gcc libffi-devel pip3 install rpy2 cffi -t /lambda/python exit
Package the Layer: Compress the python directory into a zip file: cd .. zip -r lambda-layer.zip python
Upload the Layer to AWS: Go to the AWS Management Console, create a new Lambda Layer, and upload the lambda-layer.zip. Attach the layer to your Lambda function.
Option 2: Package the Function with Dependencies If you prefer not to use a Lambda Layer, you can include all dependencies directly in your function deployment package: Set Up Amazon Linux Environment:
docker run -it --rm -v $(pwd):/lambda amazonlinux:2 /bin/bash Install Dependencies Inside Docker: yum update -y yum install -y python3-pip python3-devel gcc libffi-devel pip3 install rpy2 cffi -t /lambda exit
Package Your Function: Add your Python function file (e.g., lambda_function.py) to the /lambda directory, then compress the contents:
cd lambda zip -r function.zip .
Upload to AWS Lambda: Upload the function.zip file directly to your Lambda function.