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How to use Parameters in AWS CDK Python

Python

This is a repository to rewrite bobbyhadz/aws-cdk-parameters-example (TypeScript) in Python.
Please checkout bobbyhadz/aws-cdk-parameters-example (Typescript) and How to use Parameters in AWS CDK - Complete Guide (2021-04-23), if you want to see the original source code.

How to use

The cdk.json file tells the CDK Toolkit how to execute your app.

This project is set up like a standard Python project. The initialization process also creates a virtualenv within this project, stored under the .venv directory. To create the virtualenv it assumes that there is a python3 (or python for Windows) executable in your path with access to the venv package. If for any reason the automatic creation of the virtualenv fails, you can create the virtualenv manually.

To manually create a virtualenv on MacOS and Linux:

$ python3 -m venv .venv

After the init process completes and the virtualenv is created, you can use the following step to activate your virtualenv.

$ source .venv/bin/activate

If you are a Windows platform, you would activate the virtualenv like this:

% .venv\Scripts\activate.bat

Once the virtualenv is activated, you can install the required dependencies.

$ pip install -r requirements.txt

At this point you can now synthesize the CloudFormation template for this code.

$ export CDK_DEFAULT_ACCOUNT=$(aws sts get-caller-identity --query Account --output text)
$ export CDK_DEFAULT_REGION=$(curl -s 169.254.169.254/latest/dynamic/instance-identity/document | jq -r .region)
$ cdk synth \
    --parameters databasePort=3306 \
    --parameters dynamoDBTableName=MyDynamoTable \
    --parameters favoriteRegions="us-east-1,us-west-2"

If you generate a CloudFormation template based on our current CDK app, you would see the plain CloudFormation Parameters section:

Parameters:
  databasePort:
    Type: Number
    Default: 3306
    AllowedValues:
      - "1000"
      - "3000"
      - "3306"
    Description: The database port to open for ingress connections
    MaxValue: 10000
    MinValue: 1
  dynamoDBTableName:
    Type: String
    Description: The name of the DynamoDB table
  favoriteRegions:
    Type: CommaDelimitedList
    Description: An array of regions

Use cdk deploy command to create the stack shown above.

$ cdk deploy \
    --parameters databasePort=3306 \
    --parameters dynamoDBTableName=MyDynamoTable \
    --parameters favoriteRegions="us-east-1,us-west-2"

To add additional dependencies, for example other CDK libraries, just add them to your setup.py file and rerun the pip install -r requirements.txt command.

Useful commands

  • cdk ls list all stacks in the app
  • cdk synth emits the synthesized CloudFormation template
  • cdk deploy deploy this stack to your default AWS account/region
  • cdk diff compare deployed stack with current state
  • cdk docs open CDK documentation

Enjoy!

References