With AWS CDK Python, how to create a subdirectory, import a .py, and call a method in there? - python-3.x

Question

I am attempting to get the simplest example of creating a S3 bucket with the AWS CDK Python with no luck.
I want to put the code to create the bucket in another file (which file exists in a subdirectory).
What I am doing works with every other Python project I have developed or started.
Process:
I created an empty directory: aws_cdk_python/. I then, inside that directory ran:
$cdk init --language python to layout the structure.
This created another subdirectory with the same name aws_cdk_python/, and created a single .py within that directory where I could begin adding code in the __init__(self) method (constructor)
I was able to add code there to create a S3 bucket.
Now I created a subdirectory, with an __init__.py and a file called: create_s3_bucket.py
I put the code to create a S3 bucket in this file, in a method called 'main'
file: create_s3_bucket.py
def main(self):
<code to create s3 bucket here>
When I run the code, it will create the App Stack with no errors, but the S3 bucket will not be created.
Here is my project layout:
aws_cdk_python/
setup.py
aws_cdk_python/
aws_cdk_python_stack.py
my_aws_s3/
create_s3_bucket.py
setup.py contains the following two lines:
package_dir={"": "aws_cdk_python"},
packages=setuptools.find_packages(where="aws_cdk_python"),
The second line here says to look in the aws_cdk_python/ directory, and search recursively in sub-folders for .py files
In aws_cdk_python_stack.py, I have this line:
from my_aws_s3.create_s3_bucket import CreateS3Bucket
then in __init__ in aws_cdk_python_stack.py, I instantiate the object:
my_aws_s3 = CreateS3Bucket()
and then I make a call like so:
my_aws_s3.main() <== code to create the S3 bucket is here
I have followed this pattern on numerous Python projects before using find_packages() in setup.py
I have also run:
$python -m pip install -r requirements.txt which should pick up the dependencies pointed to in setup.py
Questions:
- Does anyone that uses the AWS CDK Python done this? or have recommendations for code organization?
I do not want all the code for the entire stack to be in aws_cdk_python_stack.py __init__() method.
Any ideas on why there no error displayed in my IDE? All dependencies are resolved, and methods found, but when I run, nothing happens?
How can I see any error messages, no error messages appear with $cdk deploy, it just creates the stack, but not the S3 bucket, even though I have code to call and create a S3 bucket.
This is frustrating, it should work.
I have other sub-directories that I want to create under aws_cdk_python/aws_cdk_python/<dir> , put a __init__.py there (empty file) and import classes in the top level aws_cdk_python_stack.py
any help to get this working would be greatly appreciated.
cdk.json looks like this (laid down from cdk init --language python
{
"app": "python app.py",
"context": {
"#aws-cdk/aws-apigateway:usagePlanKeyOrderInsensitiveId": true,
"#aws-cdk/core:enableStackNameDuplicates": "true",
"aws-cdk:enableDiffNoFail": "true",
"#aws-cdk/core:stackRelativeExports": "true",
"#aws-cdk/aws-ecr-assets:dockerIgnoreSupport": true,
"#aws-cdk/aws-secretsmanager:parseOwnedSecretName": true,
"#aws-cdk/aws-kms:defaultKeyPolicies": true,
"#aws-cdk/aws-s3:grantWriteWithoutAcl": true,
"#aws-cdk/aws-ecs-patterns:removeDefaultDesiredCount": true,
"#aws-cdk/aws-rds:lowercaseDbIdentifier": true,
"#aws-cdk/aws-efs:defaultEncryptionAtRest": true,
"#aws-cdk/aws-lambda:recognizeVersionProps": true,
"#aws-cdk/aws-cloudfront:defaultSecurityPolicyTLSv1.2_2021": true
}
}
app.py looks like this
import os
from aws_cdk import core as cdk
from aws_cdk import core
from aws_cdk_python.aws_cdk_python_stack import AwsCdkPythonStack
app = core.App()
AwsCdkPythonStack(app, "AwsCdkPythonStack",
)
app.synth()
to date: Tue 2021-12-31, this has not been solved

Answer 1

Not entirely sure, but I guess it depends on what your cdk.json file looks like. It contains the command to run for cdk deploy. E.g.:
{
"app": "python main.py", <===== this guy over here assumes the whole app is instantiated by running main.py
"context": {
...
}
}
Since I don't see this entrypoint present in your project structure it might be related to that.
Usually after running cdk init you should at least be able to synthesize. usually in app.py you keep your main App() definition and stack and constructs go in subfolders. Stacks are often instantiated in app.py and the constructs are instantiated in the stack definition files.
I hope it helped you a bit further!
Edit:
Just an example of a working tree is shown below:
aws_cdk_python
├── README.md
├── app.py
├── cdk.json
├── aws_cdk_python
│   ├── __init__.py
│   ├── example_stack.py
│   └── s3_stacks <= this is your subfolder with s3 stacks
│   ├── __init__.py
│   └── s3_stack_definition.py <== file with an s3 stack in it
├── requirements.txt
├── setup.py
└── source.bat
aws_cdk_python/s3_stacks/s3_stack_definition.py:
from aws_cdk import core as cdk
from aws_cdk import aws_s3
class S3Stack(cdk.Stack):
def __init__(self, scope: cdk.Construct, construct_id: str, **kwargs) -> None:
super().__init__(scope, construct_id, **kwargs)
bucket = aws_s3.Bucket(self, "MyEncryptedBucket",
encryption=aws_s3.BucketEncryption.KMS
)
app.py:
from aws_cdk import core
from aws_cdk_python.s3_stacks.s3_stack_definition import S3Stack
app = core.App()
S3Stack(app, "ExampleStack",
)
app.synth()