Hacker News Reader

Comment by carapace | Hacker News Reader

Yeah, thanks for asking.

I've been a happy Python programmer for over fifteen years, so this comes from a place of love and respect.

Beyond roughly 150k LoC you start to run into difficulties keeping everything straight over time, especially if you use a lot of indirection or other magic. The aspects of the language that help you go fast when you're prototyping (is "RAD" still a thing? Rapid Application Development) start to trip you up when the codebase matures. There are a lot of fancy footguns in Python that catch you if you stop dancing.

Tooling is getting a little better (MyPy, et. al.) but at the same time the overhead of adding explicit type information erodes the advantages Python has over, say, Java or Haskell.

View on HN

This is true of all dynamic languages. Rails codebases become a nightmare beyond a certain LOC. It’s taken a long time but now that we have languages with strong static typing but good type inference like Kotlin, Swift, Typescript etc the old fully dynamic languages are obsolete technology and will eventually be replaced.

from personal experience with mypy, the great thing about gradual typing in a dynamic language is that, well, it's gradual! when I want to do something extremely dynamic, there's no horrible reflection API in my way. but most of the time I can live happily inside the walled garden mypy provides.

I have adopted this attitude for personal projects & small companies, and it was mostly great.

There was at least 1 really large error that slipped into production because we were mocking an untyped service incorrectly (a mistyped property name), and the test passed, but prod exploded. It was embarrassing, and I certainly would have caught it with more mypy discipline, but overall the pros outweighed the cons.

At big companies that use mypy, however, this is problematic. If teams only define types for the straightforward parts of the system, then the types become less useful, especially as the company scales. From what I’ve seen, individual teams use an all-or-nothing approach with MyPy, so it’s unusual for an individual dev to sparsely type anything.

agreed - I am thinking more in terms of the common distinction between infrastructure/libraries and application code - I can write dynamic, well-tested libraries that are used by heavily annotated, checked application code. The types are generally more meaningful at that layer, and it tends to evolve more quickly anyway.

Reply on news.ycombinator.com