AWS CDK AWS Lambda Constructs (v1)

Common errors

• ModuleNotFoundError: No module named 'aws_cdk.core'

  cause When using AWS CDK v1, core constructs like `App` and `Stack` reside in the `aws-cdk.core` package, which must be installed separately from `aws-cdk-aws-lambda`.
  fix Ensure both `aws-cdk-aws-lambda` and `aws-cdk.core` are installed: `pip install aws-cdk-aws-lambda==1.204.0 aws-cdk.core==1.204.0`. Also, verify your imports use `from aws_cdk import core as cdk`.

• TypeError: Parameter 'runtime' for Function must be of type Runtime

  cause The `runtime` parameter for `lambda_.Function` expects an enum member from `lambda_.Runtime` (e.g., `lambda_.Runtime.PYTHON_3_9`), not a plain string.
  fix Replace string literals with the correct enum value: `runtime=lambda_.Runtime.PYTHON_3_9`.

• SynthError: Stack 'MyV1LambdaStack' contains no assets. Run 'cdk synth' to create assets for deployment.

  cause This typically means the CDK could not locate the source code for your Lambda function (`code` property), or there was an issue bundling local dependencies into the deployment package.
  fix Verify that the `code` property correctly points to your Lambda's source (e.g., `lambda_.Code.from_asset('./lambda_src')` or `lambda_.Code.from_inline(...)`). If using `from_asset`, ensure the specified path exists and contains the handler file. Check for any errors during the `cdk synth` command that might indicate bundling issues.

Warnings

• breaking AWS CDK v1 is officially deprecated and no longer receives new features or critical updates. All new development should use AWS CDK v2 (`aws-cdk-lib`). Migrating from v1 to v2 involves significant import changes and potential refactoring.
  Fix: Plan a migration to AWS CDK v2 (`pip install aws-cdk-lib` and `npm install -g aws-cdk`). Refer to the official AWS CDK migration guide for detailed steps (docs.aws.amazon.com/cdk/v2/guide/migrating-v2.html).
• gotcha Python's built-in `lambda` keyword conflicts with the `aws_lambda` module name. Always alias `aws_lambda` to `lambda_` (with an underscore) to avoid syntax errors and ensure your code is readable.
  Fix: Use `from aws_cdk import aws_lambda as lambda_` (for v1) or `from aws_cdk_lib import aws_lambda as lambda_` (for v2) when importing the Lambda constructs.
• gotcha Managing dependencies for Lambda functions requires specific packaging strategies. Simply `pip install` in your CDK project's environment will not bundle external libraries into the Lambda's deployment package.
  Fix: For local dependencies, place them in the same directory as your handler or use `lambda_.Code.from_asset('path/to/my_lambda_code', bundling={...})`. For common libraries, consider using `lambda_.LayerVersion`.
• gotcha The Python runtime versions supported by AWS Lambda constructs are tied to actual AWS Lambda service support. Using an older `Runtime` enum (e.g., `PYTHON_3_7` for a new deployment) might lead to deprecation warnings or prevent future updates as AWS phases out older runtimes.
  Fix: Always use the latest stable and supported Python runtime for your Lambda functions (e.g., `lambda_.Runtime.PYTHON_3_9` or `PYTHON_3_10` depending on the CDK version and current AWS support) unless there's a strong reason for an older one.

Install

• pip install aws-cdk-aws-lambda==1.204.0 aws-cdk.core==1.204.0 Install specific v1 Python packages
• npm install -g aws-cdk@1 Install the AWS CDK v1 CLI (required for deployment)

Imports

• Function
  wrong:

  from aws_cdk_lib import aws_lambda as lambda_

  correct:

  from aws_cdk import aws_lambda as lambda_

  This import style (`from aws_cdk import aws_lambda`) is for AWS CDK v1. The `aws_cdk.core` module is also often imported as `cdk` alongside. For v2, you import `aws_lambda` directly from the unified `aws_cdk_lib` package.
• Stack
  wrong:

  from aws_cdk import Stack

  correct:

  from aws_cdk import core as cdk

  In AWS CDK v1, `Stack` and `App` are located within the `aws_cdk.core` module, typically imported as `cdk`. Importing `Stack` directly from `aws_cdk` is the convention for AWS CDK v2, which uses the `aws-cdk-lib` package.

Quickstart

This quickstart demonstrates how to define a basic AWS Lambda function using `aws-cdk-aws-lambda` (v1) in Python. It creates a `cdk.Stack` and then adds a `lambda_.Function` with inline code. Ensure you have the AWS CDK v1 CLI and Python packages installed, and your AWS credentials configured, then run `cdk deploy` from your terminal in the directory where this code is saved (e.g., in `app.py`).

import os
from aws_cdk import (
    core as cdk, # For App, Stack
    aws_lambda as lambda_,
)
from constructs import Construct

class MyLambdaStack(cdk.Stack):
    def __init__(self, scope: Construct, construct_id: str, **kwargs) -> None:
        super().__init__(scope, construct_id, **kwargs)

        lambda_.Function(
            self, "MyHelloWorldFunction",
            runtime=lambda_.Runtime.PYTHON_3_9,
            handler="main.handler",
            code=lambda_.Code.from_inline(
                "import json\n"
                "def handler(event, context):\n"
                "    return {\n"
                "        'statusCode': 200,\n"
                "        'body': json.dumps('Hello from CDK Lambda (v1)!')\n"
                "    }"
            ),
            environment={"GREETING": os.environ.get('LAMBDA_GREETING', 'World')}
        )

# Instantiate the app and stack
app = cdk.App()
MyLambdaStack(app, "MyV1LambdaStack", env=cdk.Environment(
    account=os.environ.get('CDK_DEFAULT_ACCOUNT'),
    region=os.environ.get('CDK_DEFAULT_REGION')
))
app.synth()