AWS Compute Blog

Python 3.10 runtime now available in AWS Lambda

This post is written by Suresh Poopandi, Senior Solutions Architect, Global Life Sciences.

AWS Lambda now supports Python 3.10 as both a managed runtime and container base image. With this release, Python developers can now take advantage of new features and improvements introduced in Python 3.10 when creating serverless applications on Lambda.

Enhancements in Python 3.10 include structural pattern matching, improved error messages, and performance enhancements. This post outlines some of the benefits of Python 3.10 and how to use this version in your Lambda functions.

AWS has also published a preview Lambda container base image for Python 3.11. Customers can use this image to get an early look at Python 3.11 support in Lambda. This image is subject to change and should not be used for production workloads. To provide feedback on this image, and for future updates on Python 3.11 support, see

What’s new in Python 3.10

Thanks to its simplicity, readability, and extensive community support, Python is a popular language for building serverless applications. The Python 3.10 release includes several new features, such as:

  • Structural pattern matching (PEP 634): Structural pattern matching is one of the most significant additions to Python 3.10. With structural pattern matching, developers can use patterns to match against data structures such as lists, tuples, and dictionaries and run code based on the match. This feature enables developers to write code that processes complex data structures more easily and can improve code readability and maintainability.
  • Parenthesized context managers (BPO-12782): Python 3.10 introduces a new syntax for parenthesized context managers, making it easier to read and write code that uses the “with” statement. This feature simplifies managing resources such as file handles or database connections, ensuring they are released correctly.
  • Writing union types as X | Y (PEP 604): Python 3.10 allows writing union types as X | Y instead of the previous versions’ syntax of typing Union[X, Y]. Union types represent a value that can be one of several types. This change does not affect the functionality of the code and is backward-compatible, so code written with the previous syntax will still work. The new syntax aims to reduce boilerplate code, and improve readability and maintainability of Python code by providing a more concise and intuitive syntax for union types.
  • User-defined type guards (PEP 647): User-defined type guards allow developers to define their own type guards to handle custom data types or to refine the types of built-in types. Developers can define their own functions that perform more complex type checks as user-defined typed guards. This feature improves Python code readability, maintainability, and correctness, especially in projects with complex data structures or custom data types.
  • Improved error messages: Python 3.10 has improved error messages, providing developers with more information about the source of the error and suggesting possible solutions. This helps developers identify and fix issues more quickly. The improved error messages in Python 3.10 include more context about the error, such as the line number and location where the error occurred, as well as the exact nature of the error. Additionally, Python 3.10 error messages now provide more helpful information about how to fix the error, such as suggestions for correct syntax or usage.

Performance improvements

The faster PEP 590 vectorcall calling convention allows for quicker and more efficient Python function calls, particularly those that take multiple arguments. The specific built-in functions that benefit from this optimization include map(), filter(), reversed(), bool(), and float(). By using the vectorcall calling convention, according to Python 3.10 release notes, these inbuilt functions’ performance improved by a factor of 1.26x.

When a function is defined with annotations, these are stored in a dictionary that maps the parameter names to their respective annotations. In previous versions of Python, this dictionary was created immediately when the function was defined. However, in Python 3.10, this dictionary is created only when the annotations are accessed, which can happen when the function is called. By delaying the creation of the annotation dictionary until it is needed, Python can avoid the overhead of creating and initializing the dictionary during function definition. This can result in a significant reduction in CPU time, as the dictionary creation can be a time-consuming operation, particularly for functions with many parameters or complex annotations.

In Python 3.10, the LOAD_ATTR instruction, which is responsible for loading attributes from objects in the code, has been improved with a new mechanism called the “per opcode cache”. This mechanism works by storing frequently accessed attributes in a cache specific to each LOAD_ATTR instruction, which reduces the need for repeated attribute lookups. As a result of this improvement, according to Python 3.10 release notes, the LOAD_ATTR instruction is now approximately 36% faster when accessing regular attributes and 44% faster when accessing attributes defined using the slots mechanism.

In Python, the str(), bytes(), and bytearray() constructors are used to create new instances of these types from existing data or values. Based on the result of the performance tests conducted as part of  BPO-41334, constructors str(), bytes(), and bytearray() are around 30–40% faster for small objects.

Lambda functions developed with Python that read and process Gzip compressed files can gain a performance improvement. Adding _BlocksOutputBuffer for the bz2/lzma/zlib module eliminated the overhead of resizing bz2/lzma buffers, preventing excessive memory footprint of the zlib buffer. According to Python 3.10 release notes, bz2 decompression is now 1.09x faster, lzma decompression 1.20x faster, and GzipFile read is 1.11x faster

Using Python 3.10 in Lambda

AWS Management Console

To use the Python 3.10 runtime to develop your Lambda functions, specify a runtime parameter value Python 3.10 when creating or updating a function. Python 3.10 version is now available in the Runtime dropdown in the Create function page.

Lambda create function page

To update an existing Lambda function to Python 3.10, navigate to the function in the Lambda console, then choose Edit in the Runtime settings panel. The new version of Python is available in the Runtime dropdown:

Edit runtime settings

AWS Serverless Application Model (AWS SAM)

In AWS SAM, set the Runtime attribute to python3.10 to use this version.

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: Simple Lambda Function
    Type: AWS::Serverless::Function
      Description: My Python Lambda Function
      CodeUri: my_function/
      Handler: lambda_function.lambda_handler
      Runtime: python3.10

AWS SAM supports the generation of this template with Python 3.10 out of the box for new serverless applications using the sam init command. Refer to the AWS SAM documentation here.

AWS Cloud Development Kit (AWS CDK)

In the AWS CDK, set the runtime attribute to Runtime.PYTHON_3_10 to use this version. In Python:

from constructs import Construct
from aws_cdk import (
    App, Stack,
    aws_lambda as _lambda

class SampleLambdaStack(Stack):

    def __init__(self, scope: Construct, id: str, **kwargs) -> None:
        super().__init__(scope, id, **kwargs)

        base_lambda = _lambda.Function(self, 'SampleLambda',

In TypeScript:

import * as cdk from 'aws-cdk-lib';
import * as lambda from 'aws-cdk-lib/aws-lambda'
import * as path from 'path';
import { Construct } from 'constructs';

export class CdkStack extends cdk.Stack {
  constructor(scope: Construct, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

    // The code that defines your stack goes here

    // The python3.10 enabled Lambda Function
    const lambdaFunction = new lambda.Function(this, 'python310LambdaFunction', {
      runtime: lambda.Runtime.PYTHON_3_10,
      memorySize: 512,
      code: lambda.Code.fromAsset(path.join(__dirname, '/../lambda')),
      handler: 'lambda_handler.handler'

AWS Lambda – Container Image

Change the Python base image version by modifying FROM statement in the Dockerfile:


# Copy function code

To learn more, refer to the usage tab on building functions as container images.


You can build and deploy functions using Python 3.10 using the AWS Management ConsoleAWS CLIAWS SDKAWS SAM, AWS CDK, or your choice of Infrastructure as Code (IaC). You can also use the Python 3.10 container base image if you prefer to build and deploy your functions using container images.

We are excited to bring Python 3.10 runtime support to Lambda and empower developers to build more efficient, powerful, and scalable serverless applications. Try Python 3.10 runtime in Lambda today and experience the benefits of this updated language version and take advantage of improved performance.

For more serverless learning resources, visit Serverless Land.