mypy-boto3-lambda Type Annotations

1.42.85 · active · verified Thu Apr 09

mypy-boto3-lambda provides type annotations for the AWS Lambda client in `boto3`, generated by `mypy-boto3-builder`. It enhances type checking for `boto3` usage, preventing common runtime errors related to incorrect AWS service calls or response parsing. The library version `1.42.85` corresponds to `boto3` version `1.42.85`. New versions are released frequently, typically mirroring `boto3` releases.

Warnings

breaking Support for Python 3.8 was removed. Packages generated by `mypy-boto3-builder` v8.12.0 and later (which includes `mypy-boto3-lambda` v1.42.85) require Python 3.9 or higher.
Fix: Upgrade your Python environment to 3.9 or newer. If you must use Python 3.8, you'll need to pin to older `mypy-boto3-lambda` versions, though this is not recommended due to potential `boto3` mismatches.
breaking The `sms-voice` service was deprecated and renamed to `pinpoint-sms-voice`. Direct usage of the `sms-voice` client will fail.
Fix: Update your code to use `boto3.client("pinpoint-sms-voice")` instead of `boto3.client("sms-voice")`.
breaking TypeDef names for packed method arguments changed, becoming shorter (e.g., `CreateDistributionRequestRequestTypeDef` -> `CreateDistributionRequestTypeDef`). Conflicting TypeDef `Extra` postfixes also moved.
Fix: Review and update explicit TypeDef annotations in your code to match the new naming conventions, or rely on implicit typing where possible and let `mypy` infer the correct types.
gotcha This package provides only type stubs. It is not the `boto3` library itself. You must install `boto3` separately for your code to function at runtime.
Fix: Ensure `boto3` is included in your project's dependencies: `pip install boto3 mypy-boto3-lambda`.
gotcha The `mypy-boto3-*` stub packages are versioned to align with specific `boto3` versions. Using mismatched versions (e.g., `mypy-boto3-lambda` 1.42.85 with `boto3` 1.20.0) can lead to incorrect type hints or `mypy` errors.
Fix: Always try to keep your `mypy-boto3-*` stub versions as close as possible to your `boto3` version. The recommended approach is to install the latest versions of both.

Install

pip install mypy-boto3-lambda boto3 Install stubs and boto3

Imports

LambdaClient
```
from mypy_boto3_lambda.client import LambdaClient
```
Used for explicit type hinting of the Lambda client object.
ListFunctionsResponseTypeDef
```
from mypy_boto3_lambda.type_defs import ListFunctionsResponseTypeDef
```
Used for explicit type hinting of method response objects.

Quickstart

This example demonstrates how to create a type-hinted `boto3` Lambda client. `mypy` will automatically pick up the installed stubs when `boto3.client('lambda')` is called, providing autocompletion and type validation. Explicit imports for `LambdaClient` and response `TypeDef` are used for clearer annotations.

import boto3
from mypy_boto3_lambda.client import LambdaClient
from mypy_boto3_lambda.type_defs import ListFunctionsResponseTypeDef

# Create a typed Lambda client
# mypy will automatically use the installed mypy-boto3-lambda stubs for type checking
lambda_client: LambdaClient = boto3.client("lambda")

try:
    # Example: List Lambda functions
    # The response object will be correctly typed
    response: ListFunctionsResponseTypeDef = lambda_client.list_functions(MaxItems=1)
    print("Successfully listed Lambda functions (first item): ")
    for func in response.get("Functions", []):
        print(f"- {func['FunctionName']}")
except Exception as e:
    # This may happen if AWS credentials are not configured or if the user lacks permissions.
    print(f"Error listing Lambda functions: {e}")
    print("Ensure your AWS credentials are configured (e.g., via AWS CLI or environment variables).")

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