How do I know which version of Powertools is in the Lambda layer?

[iainelder]

When I started working with Powertools in January this year, I copied a layer ARN from the documentation homepage.

arn:aws:lambda:eu-central-1:017000801446:layer:AWSLambdaPowertoolsPythonV3-python312-arm64:7

The last part of the ARN means it was layer version 7.

Today the documentation shows this ARN:

arn:aws:lambda:eu-central-1:017000801446:layer:AWSLambdaPowertoolsPythonV3-python312-arm64:12

The last part of the ARN means layer version 12.

How do I correspond the layer version to the semantic version of the library?

The semantic versions look like this: 3.8.0, 3.9.0, 3.10.0.

I see another discussion from 2023 where it seems a maintainer decided against documenting the content of the layer in favor of allowing a user to "peek into the contents" of the layer. I hope this isn't the only way, because it not at all clear whether it will help me answer my question.

#1807 (reply in thread)

[iainelder]

I scripted the Lambda Layers API to find the solution.

LayerVersion	LayerVersionCreatedDate	PowertoolsVersion
1	2024-09-23	3.0.0
2	2024-10-08	3.1.0
3	2024-10-22	3.2.0
4	2024-11-14	3.3.0
5	2024-12-20	3.4.0
6	2025-01-14	3.4.1
7	2025-01-28	3.5.0
8	2025-02-11	3.6.0
9	2025-02-25	3.7.0
10	2025-03-07	3.8.0
11	2025-03-25	3.9.0
12	2025-04-08	3.10.0

To reproduce, run this code in Bash.

get-powertools-version-for-layer-version() {
    layer="arn:aws:lambda:eu-central-1:017000801446:layer:AWSLambdaPowertoolsPythonV3-python312-arm64"
    version="$1"

    aws lambda get-layer-version-by-arn --arn "$layer:$version" |
    jq -c '{
        LayerVersion: .Version | tostring,
        LayerVersionCreatedDate: .CreatedDate[0:10],
        PowertoolsVersion: .Description | split(" ") | .[-1]
    }'
}

export -f get-powertools-version-for-layer-version

seq 1 12 | parallel -k get-powertools-version-for-layer-version | jtbl -m

As well as the AWS CLI, you'll need more tools: jq, seq, parallel, and jtbl.

You also need programmatic access to an AWS account with a policy that allows you to perform the AWS actions.

[leandrodamascena]

Hi @iainelder! Another way to achieve this is by using SSM Parameters, where you can query the semantic version and find out the corresponding layer ARN. We have published public parameters for Powertools, so you can query using the aws ssm command:

aws ssm get-parameter --name /aws/service/powertools/python/arm64/python3.11/3.10.0 --region REGION

it will output:

{
    "Parameter": {
        "Name": "/aws/service/powertools/python/arm64/python3.11/3.10.0",
        "Type": "String",
        "Value": "arn:aws:lambda:us-east-1:017000801446:layer:AWSLambdaPowertoolsPythonV3-python311-arm64:12",
        "Version": 1,
        "LastModifiedDate": "2025-04-08T14:21:51.392000+01:00",
        "ARN": "arn:aws:ssm:us-east-1::parameter/aws/service/powertools/python/arm64/python3.11/3.10.0",
        "DataType": "text"
    }
}

Value corresponds to the layer ARN for that specific semantic version. If you want the latest version of powertools, then replace 3.10.0 with latest.

possible values for architecture: arm64 and x86_64
possible values for Python versions: python3.9, python3.10, python3.11, python3.12 and python3.13

[iainelder]

Thanks, @leandrodamascena . This is an easier way to determine programmatically which layer version to use to support a given semantic version.

It would be great to see that in the documentation. I couldn't find it when I searched for "public parameters".

[leandrodamascena]

Hey @iainelder, we have it here: https://docs.powertools.aws.dev/lambda/python/latest/#aws-ssm-parameter-store

But I agree this is hard to find in the documentation. I'll work to refactor the homepage soon. Thanks a lot for your inputs.

[iainelder]

It would be great to see that information baked into the documentation so that I know exactly which layer I need to use based on the Powertools version I need to support.

[iainelder]

The documentation already has the data, but not all in one place.

Each semantic version's homepage shows the layer version that supports it.

The page for 3.10.0 shows layer version 12, The page for 3.9.0 shows layer version 11, and so on as described in the table above.