ART: CDK new app

content/aws/50005000-cdk-new-app.md

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+Title: Creating a new CDK app with Python
+Date: 2023-10-22
+Category: AWS Academy
+Series: AWS CDK
+series_index: 4
+Tags: aws, cdk
+Author: Rehan Haider
+Summary: How to create a new CDK app that uses Python as the programming language
+Keywords: AWS
+
+
+In this post, we'll create a new CDK app that uses Python as the programming language. 
+
+!!! note
+    Ensure that [AWS CDK is installed & configured]({filename}00000100-cdk-installing-cdk-sam-cli.md) before proceeding.
+
+
+## Creating a new CDK app
+
+a) Create a new directory for the CDK app and navigate to it:
+
+```bash
+mkdir cdk-app && cd cdk-app
+```
+
+
+b) To create a new CDK app, run the following command:
+
+```bash
+cdk init app --language python
+```
+
+The above command will create the following:
+
+1. **CDK App**: Create a new CDK app in the current directory. It includes a `cdk.json` file that includes the configuration for the CDK app
+2. **Stacks**: Create a folder called `cdk-app` in the current directory that includes the `stacks` that will be deployed
+3. **Python Virtual Environment**: Create a Python virtual environment for the app in the .venv folder. It also creates a `requirements.txt` file that includes the Python dependencies for the app
+4. **Git**: Create a git repository for the app including a `.gitignore` file
+
+
+c) Activate the Python virtual environment:
+
+```bash
+source .venv/bin/activate
+```
+
+If you are using Windows, run the following command instead:
+
+```powershell
+./source.bat
+```
+
+d) Install the Python dependencies:
+
+```bash
+pip install -r requirements.txt -r requirements-dev.txt
+```
+
+## Modifying the CDK app
+
+a) Open the `app.py` file. This file includes the basic CDK app that includes a single stack called `CdkAppStack`. 
+
+```python
+import os
+import aws_cdk as cdk
+
+from cdk_app.cdk_app_stack import CdkAppStack
+
+
+app = cdk.App()
+CdkAppStack(app, "CdkAppStack",)
+
+app.synth()
+```
+
+In the above code, we are importing the `CdkAppStack` class from the `cdk_app_stack.py` file. This file is located in the `cdk_app` folder.
+
+b) Open the `cdk_app_stack.py` file. This file includes the `CdkAppStack` class that extends the `cdk.Stack` class. 
+
+```python
+from aws_cdk import (
+    Stack,
+)
+from constructs import Construct
+
+class CdkAppStack(Stack):
+
+    def __init__(self, scope: Construct, construct_id: str, **kwargs) -> None:
+        super().__init__(scope, construct_id, **kwargs)
+
+        # The code that defines your stack goes here
+
+```
+
+Currently, the `CdkAppStack` class does not include any resources. Let's add a S3 bucket to the stack.
+
+c) Modify the `cdk_app_stack.py` file as follows:
+
+```python
+from aws_cdk import (
+    Stack,
+    aws_s3 as s3,
+)
+
+from constructs import Construct
+
+class CdkAppStack(Stack):
+
+    BUCKET_NAME = "MyFirstBucket"
+
+    def __init__(self, scope: Construct, construct_id: str, **kwargs) -> None:
+        super().__init__(scope, construct_id, **kwargs)
+
+        # The code that defines your stack goes here
+        s3.Bucket(self, id=self.BUCKET_NAME)
+
+```
+Change the `BUCKET_NAME` variable to a name of your choice. This is not the name of the S3 bucket but the ID by which the S3 bucket will be referenced in the CDK app.
+
+## Deploying the CDK app
+
+a) Run `cdk synth` to synthesize the CDK app. Synth will generate a CloudFormation template for the CDK app. You can see the generated template in the `cdk.out` folder.
+
+b) Run `cdk deploy` to deploy the CDK app. CDK will deploy the S3 bucket to your AWS account. You can see the deployed S3 bucket in the AWS Console.
+
+![Deployed S3 bucket]({static}/images/aws-academy/50005000-cdk-deploy-cloudformation.png)
+
+You can see the deployed S3 bucket in the AWS Console.
+
+## Destroying the CDK app
+
+To destroy the CDK app, run the following command:
+
+```bash
+cdk destroy
+```
+
+However, this will not delete the S3 bucket. You have to manually delete the S3 bucket from the AWS Console.
+This is the default behaviour of CDK so you don't accidentally delete S3 buckets that contain important data.