There are three ways to build a container image for a Python Lambda function:
This page explains how to build, test, and deploy container images for Lambda.
AWS base images for PythonAWS provides the following base images for Python:
Amazon ECR repository: gallery.ecr.aws/lambda/python
Python 3.12 and later base images are based on the Amazon Linux 2023 minimal container image. The Python 3.8-3.11 base images are based on the Amazon Linux 2 image. AL2023-based images provide several advantages over Amazon Linux 2, including a smaller deployment footprint and updated versions of libraries such as glibc
.
AL2023-based images use microdnf
(symlinked as dnf
) as the package manager instead of yum
, which is the default package manager in Amazon Linux 2. microdnf
is a standalone implementation of dnf
. For a list of packages that are included in AL2023-based images, refer to the Minimal Container columns in Comparing packages installed on Amazon Linux 2023 Container Images. For more information about the differences between AL2023 and Amazon Linux 2, see Introducing the Amazon Linux 2023 runtime for AWS Lambda on the AWS Compute Blog.
To run AL2023-based images locally, including with AWS Serverless Application Model (AWS SAM), you must use Docker version 20.10.10 or later.
Dependency search path in the base imagesWhen you use an import
statement in your code, the Python runtime searches the directories in its search path until it finds the module or package. By default, the runtime searches the {LAMBDA_TASK_ROOT}
directory first. If you include a version of a runtime-included library in your image, your version will take precedence over the version that's included in the runtime.
Other steps in the search path depend on which version of the Lambda base image for Python you're using:
Python 3.11 and later: Runtime-included libraries and pip-installed libraries are installed in the /var/lang/lib/python3.11/site-packages
directory. This directory has precedence over /var/runtime
in the search path. You can override the SDK by using pip to install a newer version. You can use pip to verify that the runtime-included SDK and its dependencies are compatible with any packages that you install.
Python 3.8-3.10: Runtime-included libraries are installed in the /var/runtime
directory. Pip-installed libraries are installed in the /var/lang/lib/python3.x/site-packages
directory. The /var/runtime
directory has precedence over /var/lang/lib/python3.x/site-packages
in the search path.
You can see the full search path for your Lambda function by adding the following code snippet.
import sys
search_path = sys.path
print(search_path)
Using an AWS base image for Python
To complete the steps in this section, you must have the following:
To create a container image from an AWS base image for PythonCreate a directory for the project, and then switch to that directory.
mkdir example
cd example
Create a new file called lambda_function.py
. You can add the following sample function code to the file for testing, or use your own.
import sys
def handler(event, context):
return 'Hello from AWS Lambda using Python' + sys.version + '!'
Create a new file called requirements.txt
. If you're using the sample function code from the previous step, you can leave the file empty because there are no dependencies. Otherwise, list each required library. For example, here's what your requirements.txt
should look like if your function uses the AWS SDK for Python (Boto3):
Create a new Dockerfile with the following configuration:
Note that the example Dockerfile does not include a USER instruction. When you deploy a container image to Lambda, Lambda automatically defines a default Linux user with least-privileged permissions. This is different from standard Docker behavior which defaults to the root
user when no USER
instruction is provided.
FROM public.ecr.aws/lambda/python:3.12
# Copy requirements.txt
COPY requirements.txt ${LAMBDA_TASK_ROOT}
# Install the specified packages
RUN pip install -r requirements.txt
# Copy function code
COPY lambda_function.py ${LAMBDA_TASK_ROOT}
# Set the CMD to your handler (could also be done as a parameter override outside of the Dockerfile)
CMD [ "lambda_function.handler" ]
Build the Docker image with the docker build command. The following example names the image docker-image
and gives it the test
tag. To make your image compatible with Lambda, you must use the --provenance=false
option.
docker buildx build --platform linux/amd64 --provenance=false -t docker-image
:test
.
Note
The command specifies the --platform linux/amd64
option to ensure that your container is compatible with the Lambda execution environment regardless of the architecture of your build machine. If you intend to create a Lambda function using the ARM64 instruction set architecture, be sure to change the command to use the --platform linux/arm64
option instead.
Start the Docker image with the docker run command. In this example, docker-image
is the image name and test
is the tag.
docker run --platform linux/amd64 -p 9000:8080 docker-image
:test
This command runs the image as a container and creates a local endpoint at localhost:9000/2015-03-31/functions/function/invocations
.
If you built the Docker image for the ARM64 instruction set architecture, be sure to use the --platform linux/
option instead of arm64
--platform linux/
.amd64
From a new terminal window, post an event to the local endpoint.
In Linux and macOS, run the following curl
command:
curl "http://localhost:9000/2015-03-31/functions/function/invocations" -d '{}'
This command invokes the function with an empty event and returns a response. If you're using your own function code rather than the sample function code, you might want to invoke the function with a JSON payload. Example:
curl "http://localhost:9000/2015-03-31/functions/function/invocations" -d '{"payload":"hello world!"}
'
In PowerShell, run the following Invoke-WebRequest
command:
Invoke-WebRequest -Uri "http://localhost:9000/2015-03-31/functions/function/invocations" -Method Post -Body '{}' -ContentType "application/json"
This command invokes the function with an empty event and returns a response. If you're using your own function code rather than the sample function code, you might want to invoke the function with a JSON payload. Example:
Invoke-WebRequest -Uri "http://localhost:9000/2015-03-31/functions/function/invocations" -Method Post -Body '{"payload":"hello world!"}
' -ContentType "application/json"
Get the container ID.
docker ps
Use the docker kill command to stop the container. In this command, replace 3766c4ab331c
with the container ID from the previous step.
docker kill 3766c4ab331c
Run the get-login-password command to authenticate the Docker CLI to your Amazon ECR registry.
Set the --region
value to the AWS Region where you want to create the Amazon ECR repository.
Replace 111122223333
with your AWS account ID.
aws ecr get-login-password --region us-east-1
| docker login --username AWS --password-stdin 111122223333
.dkr.ecr.us-east-1
.amazonaws.com
Create a repository in Amazon ECR using the create-repository command.
aws ecr create-repository --repository-name hello-world
--region us-east-1
--image-scanning-configuration scanOnPush=true --image-tag-mutability MUTABLE
Note
The Amazon ECR repository must be in the same AWS Region as the Lambda function.
If successful, you see a response like this:
{
"repository": {
"repositoryArn": "arn:aws:ecr:us-east-1:111122223333:repository/hello-world",
"registryId": "111122223333",
"repositoryName": "hello-world",
"repositoryUri": "111122223333.dkr.ecr.us-east-1.amazonaws.com/hello-world",
"createdAt": "2023-03-09T10:39:01+00:00",
"imageTagMutability": "MUTABLE",
"imageScanningConfiguration": {
"scanOnPush": true
},
"encryptionConfiguration": {
"encryptionType": "AES256"
}
}
}
Copy the repositoryUri
from the output in the previous step.
Run the docker tag command to tag your local image into your Amazon ECR repository as the latest version. In this command:
docker-image:test
is the name and tag of your Docker image. This is the image name and tag that you specified in the docker build
command.
Replace <ECRrepositoryUri>
with the repositoryUri
that you copied. Make sure to include :latest
at the end of the URI.
docker tag docker-image:test <ECRrepositoryUri>
:latest
Example:
docker tag docker-image
:test
111122223333
.dkr.ecr.us-east-1
.amazonaws.com/hello-world
:latest
Run the docker push command to deploy your local image to the Amazon ECR repository. Make sure to include :latest
at the end of the repository URI.
docker push 111122223333
.dkr.ecr.us-east-1
.amazonaws.com/hello-world
:latest
Create an execution role for the function, if you don't already have one. You need the Amazon Resource Name (ARN) of the role in the next step.
Create the Lambda function. For ImageUri
, specify the repository URI from earlier. Make sure to include :latest
at the end of the URI.
aws lambda create-function \
--function-name hello-world
\
--package-type Image \
--code ImageUri=111122223333
.dkr.ecr.us-east-1
.amazonaws.com/hello-world
:latest \
--role arn:aws:iam::111122223333:role/lambda-ex
Note
You can create a function using an image in a different AWS account, as long as the image is in the same Region as the Lambda function. For more information, see Amazon ECR cross-account permissions.
Invoke the function.
aws lambda invoke --function-name hello-world
response.json
You should see a response like this:
{
"ExecutedVersion": "$LATEST",
"StatusCode": 200
}
To see the output of the function, check the response.json
file.
To update the function code, you must build the image again, upload the new image to the Amazon ECR repository, and then use the update-function-code command to deploy the image to the Lambda function.
Lambda resolves the image tag to a specific image digest. This means that if you point the image tag that was used to deploy the function to a new image in Amazon ECR, Lambda doesn't automatically update the function to use the new image.
To deploy the new image to the same Lambda function, you must use the update-function-code command, even if the image tag in Amazon ECR remains the same. In the following example, the --publish
option creates a new version of the function using the updated container image.
aws lambda update-function-code \
--function-name hello-world
\
--image-uri 111122223333.dkr.ecr.us-east-1.amazonaws.com/hello-world:latest
\
--publish
Using an alternative base image with the runtime interface client
If you use an OS-only base image or an alternative base image, you must include the runtime interface client in your image. The runtime interface client extends the Runtime API, which manages the interaction between Lambda and your function code.
Install the the runtime interface client for Python using the pip package manager:
pip install awslambdaric
You can also download the Python runtime interface client from GitHub.
The following example demonstrates how to build a container image for Python using a non-AWS base image. The example Dockerfile uses an official Python base image. The Dockerfile includes the runtime interface client for Python.
To complete the steps in this section, you must have the following:
To create a container image from a non-AWS base imageCreate a directory for the project, and then switch to that directory.
mkdir example
cd example
Create a new file called lambda_function.py
. You can add the following sample function code to the file for testing, or use your own.
import sys
def handler(event, context):
return 'Hello from AWS Lambda using Python' + sys.version + '!'
Create a new file called requirements.txt
. If you're using the sample function code from the previous step, you can leave the file empty because there are no dependencies. Otherwise, list each required library. For example, here's what your requirements.txt
should look like if your function uses the AWS SDK for Python (Boto3):
Create a new Dockerfile. The following Dockerfile uses an official Python base image instead of an AWS base image. The Dockerfile includes the runtime interface client, which makes the image compatible with Lambda. The following example Dockerfile uses a multi-stage build.
Set the FROM
property to the base image.
Set the ENTRYPOINT
to the module that you want the Docker container to run when it starts. In this case, the module is the runtime interface client.
Set the CMD
to the Lambda function handler.
Note that the example Dockerfile does not include a USER instruction. When you deploy a container image to Lambda, Lambda automatically defines a default Linux user with least-privileged permissions. This is different from standard Docker behavior which defaults to the root
user when no USER
instruction is provided.
# Define custom function directory
ARG FUNCTION_DIR="/function"
FROM python:3.12
AS build-image
# Include global arg in this stage of the build
ARG FUNCTION_DIR
# Copy function code
RUN mkdir -p ${FUNCTION_DIR}
COPY . ${FUNCTION_DIR}
# Install the function's dependencies
RUN pip install \
--target ${FUNCTION_DIR} \
awslambdaric
# Use a slim version of the base Python image to reduce the final image size
FROM python:3.12-slim
# Include global arg in this stage of the build
ARG FUNCTION_DIR
# Set working directory to function root directory
WORKDIR ${FUNCTION_DIR}
# Copy in the built dependencies
COPY --from=build-image ${FUNCTION_DIR} ${FUNCTION_DIR}
# Set runtime interface client as default command for the container runtime
ENTRYPOINT [ "/usr/local/bin/python", "-m", "awslambdaric
" ]
# Pass the name of the function handler as an argument to the runtime
CMD [ "lambda_function.handler
" ]
Build the Docker image with the docker build command. The following example names the image docker-image
and gives it the test
tag. To make your image compatible with Lambda, you must use the --provenance=false
option.
docker buildx build --platform linux/amd64 --provenance=false -t docker-image
:test
.
Note
The command specifies the --platform linux/amd64
option to ensure that your container is compatible with the Lambda execution environment regardless of the architecture of your build machine. If you intend to create a Lambda function using the ARM64 instruction set architecture, be sure to change the command to use the --platform linux/arm64
option instead.
Use the runtime interface emulator to locally test the image. You can build the emulator into your image or use the following procedure to install it on your local machine.
To install and run the runtime interface emulator on your local machineFrom your project directory, run the following command to download the runtime interface emulator (x86-64 architecture) from GitHub and install it on your local machine.
mkdir -p ~/.aws-lambda-rie && \
curl -Lo ~/.aws-lambda-rie/aws-lambda-rie https://github.com/aws/aws-lambda-runtime-interface-emulator/releases/latest/download/aws-lambda-rie && \
chmod +x ~/.aws-lambda-rie/aws-lambda-rie
To install the arm64 emulator, replace the GitHub repository URL in the previous command with the following:
https://github.com/aws/aws-lambda-runtime-interface-emulator/releases/latest/download/aws-lambda-rie-arm64
$dirPath = "$HOME\.aws-lambda-rie"
if (-not (Test-Path $dirPath)) {
New-Item -Path $dirPath -ItemType Directory
}
$downloadLink = "https://github.com/aws/aws-lambda-runtime-interface-emulator/releases/latest/download/aws-lambda-rie"
$destinationPath = "$HOME\.aws-lambda-rie\aws-lambda-rie"
Invoke-WebRequest -Uri $downloadLink -OutFile $destinationPath
To install the arm64 emulator, replace the $downloadLink
with the following:
https://github.com/aws/aws-lambda-runtime-interface-emulator/releases/latest/download/aws-lambda-rie-arm64
Start the Docker image with the docker run command. Note the following:
docker-image
is the image name and test
is the tag.
/usr/local/bin/python -m awslambdaric lambda_function.handler
is the ENTRYPOINT
followed by the CMD
from your Dockerfile.
docker run --platform linux/amd64 -d -v ~/.aws-lambda-rie:/aws-lambda -p 9000:8080 \
--entrypoint /aws-lambda/aws-lambda-rie \
docker-image:test
\
/usr/local/bin/python -m awslambdaric lambda_function.handler
docker run --platform linux/amd64 -d -v "$HOME\.aws-lambda-rie:/aws-lambda" -p 9000:8080 `
--entrypoint /aws-lambda/aws-lambda-rie `
docker-image:test
`
/usr/local/bin/python -m awslambdaric lambda_function.handler
This command runs the image as a container and creates a local endpoint at localhost:9000/2015-03-31/functions/function/invocations
.
If you built the Docker image for the ARM64 instruction set architecture, be sure to use the --platform linux/
option instead of arm64
--platform linux/
.amd64
Post an event to the local endpoint.
In Linux and macOS, run the following curl
command:
curl "http://localhost:9000/2015-03-31/functions/function/invocations" -d '{}'
This command invokes the function with an empty event and returns a response. If you're using your own function code rather than the sample function code, you might want to invoke the function with a JSON payload. Example:
curl "http://localhost:9000/2015-03-31/functions/function/invocations" -d '{"payload":"hello world!"}
'
In PowerShell, run the following Invoke-WebRequest
command:
Invoke-WebRequest -Uri "http://localhost:9000/2015-03-31/functions/function/invocations" -Method Post -Body '{}' -ContentType "application/json"
This command invokes the function with an empty event and returns a response. If you're using your own function code rather than the sample function code, you might want to invoke the function with a JSON payload. Example:
Invoke-WebRequest -Uri "http://localhost:9000/2015-03-31/functions/function/invocations" -Method Post -Body '{"payload":"hello world!"}
' -ContentType "application/json"
Get the container ID.
docker ps
Use the docker kill command to stop the container. In this command, replace 3766c4ab331c
with the container ID from the previous step.
docker kill 3766c4ab331c
Run the get-login-password command to authenticate the Docker CLI to your Amazon ECR registry.
Set the --region
value to the AWS Region where you want to create the Amazon ECR repository.
Replace 111122223333
with your AWS account ID.
aws ecr get-login-password --region us-east-1
| docker login --username AWS --password-stdin 111122223333
.dkr.ecr.us-east-1
.amazonaws.com
Create a repository in Amazon ECR using the create-repository command.
aws ecr create-repository --repository-name hello-world
--region us-east-1
--image-scanning-configuration scanOnPush=true --image-tag-mutability MUTABLE
Note
The Amazon ECR repository must be in the same AWS Region as the Lambda function.
If successful, you see a response like this:
{
"repository": {
"repositoryArn": "arn:aws:ecr:us-east-1:111122223333:repository/hello-world",
"registryId": "111122223333",
"repositoryName": "hello-world",
"repositoryUri": "111122223333.dkr.ecr.us-east-1.amazonaws.com/hello-world",
"createdAt": "2023-03-09T10:39:01+00:00",
"imageTagMutability": "MUTABLE",
"imageScanningConfiguration": {
"scanOnPush": true
},
"encryptionConfiguration": {
"encryptionType": "AES256"
}
}
}
Copy the repositoryUri
from the output in the previous step.
Run the docker tag command to tag your local image into your Amazon ECR repository as the latest version. In this command:
docker-image:test
is the name and tag of your Docker image. This is the image name and tag that you specified in the docker build
command.
Replace <ECRrepositoryUri>
with the repositoryUri
that you copied. Make sure to include :latest
at the end of the URI.
docker tag docker-image:test <ECRrepositoryUri>
:latest
Example:
docker tag docker-image
:test
111122223333
.dkr.ecr.us-east-1
.amazonaws.com/hello-world
:latest
Run the docker push command to deploy your local image to the Amazon ECR repository. Make sure to include :latest
at the end of the repository URI.
docker push 111122223333
.dkr.ecr.us-east-1
.amazonaws.com/hello-world
:latest
Create an execution role for the function, if you don't already have one. You need the Amazon Resource Name (ARN) of the role in the next step.
Create the Lambda function. For ImageUri
, specify the repository URI from earlier. Make sure to include :latest
at the end of the URI.
aws lambda create-function \
--function-name hello-world
\
--package-type Image \
--code ImageUri=111122223333
.dkr.ecr.us-east-1
.amazonaws.com/hello-world
:latest \
--role arn:aws:iam::111122223333:role/lambda-ex
Note
You can create a function using an image in a different AWS account, as long as the image is in the same Region as the Lambda function. For more information, see Amazon ECR cross-account permissions.
Invoke the function.
aws lambda invoke --function-name hello-world
response.json
You should see a response like this:
{
"ExecutedVersion": "$LATEST",
"StatusCode": 200
}
To see the output of the function, check the response.json
file.
To update the function code, you must build the image again, upload the new image to the Amazon ECR repository, and then use the update-function-code command to deploy the image to the Lambda function.
Lambda resolves the image tag to a specific image digest. This means that if you point the image tag that was used to deploy the function to a new image in Amazon ECR, Lambda doesn't automatically update the function to use the new image.
To deploy the new image to the same Lambda function, you must use the update-function-code command, even if the image tag in Amazon ECR remains the same. In the following example, the --publish
option creates a new version of the function using the updated container image.
aws lambda update-function-code \
--function-name hello-world
\
--image-uri 111122223333.dkr.ecr.us-east-1.amazonaws.com/hello-world:latest
\
--publish
For an example of how to create a Python image from an Alpine base image, see Container image support for Lambda on the AWS Blog.
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