Python CDK Setup

[dbanty]

I've recently put a bunch of work into making my APIGateway + Lambda setup in CDK work with Python applications. The hardest part was getting the dependencies all building correctly. If you're interested in a blog post / tutorial on this topic, upvote this thread! If there are specific things you'd like to see or questions you'd like answered on this topic, comment them below.

[mosheduminer]

It happens that right now I'm interested in learning about the CDK in general. Would definitely appreciate a blog post!

BTW I'm curious about typing in the python CDK. Does python's relatively immature type system result in bugs when using the CDK? What are the results?

[dbanty]

Yeah there are some rough patches for sure. CDK does include type annotations, but I think they’re all generated from the equivalent TypeScript code.

In TS, they use interfaces for props so you don’t need direct inheritance. In Python, rather than using Protocol—which is the closest equivalent to interfaces—they use a normal class. My guess is that’s to support older Python versions.

Unfortunately, even without using Protocol, they still want the flexibility of interfaces. So they don’t inherit from the not-interface in their concrete implementations. All of this is to say it looks like you’re passing in the wrong type to a lot of classes/functions, so you really can’t rely on the static types at all. Instead you get IDE/mypy errors while writing 🙁.

This was annoying enough that I actually stuck with TypeScript for writing the CDK code of my Python lambdas at work.

[mosheduminer]

All of this is to say it looks like you’re passing in the wrong type to a lot of classes/functions, so you really can’t rely on the static types at all.

This was annoying enough that I actually stuck with TypeScript for writing the CDK code of my Python lambdas at work.

This was my worst fear. When I start actually writing CDK code, I'll probably stick to TS as well.

[dbanty]

The cdk cli tool requires node anyway, so using TS doesn’t feel too bad. I just include the CLI in that same package.json.