9 ms·

Honestly, I've recently written a few 300-500 line programs in Python using type hints and I'm never going back. And I'm not even using mypy often, if ever. M

Honestly, I've recently written a few 300-500 line programs in Python using type hints and I'm never going back. And I'm not even using mypy often, if ever. My editor now has a fairly deep understanding of my code, and can tell me of all sorts of surprising errors I'm making before I run the code. There have been a few times where I found an error, went into the editor and saw I had missed a error message about that line. Shout out: Using LunarVim with LSP and TreeSitter. The other thing I'm enjoying is that libraries can use them to make things happen more automatically. I believe it was Typer (the CLI argument parsing library) where if you declare an argument to a function as "files: List[Path]", it understands that the argument will take one or more files, or "-" to mean stdin. If you just say "file: Path", it understands it is a singular file. I was curious about type hints when they first came out, wasn't really expecting to use them but they seemed cool, but now I'm totally sold.

totony 5y ago
>My editor now has a fairly deep understanding of my code, and can tell me of all sorts of surprising errors I'm making before I run the code. I agree this is useful, but to me the most useful feature of types are the self-documentation. It's crazy the difference between a non-typed library with shitty documentation vs a typed library with shitty documentation.
- kadoban 5y ago
  The types on stitty-documented code often do depend on the types actually being checked though. Otherwise you need to author to be diligent in their types, but if they're bad in their other docs, that seems unlikely.
  - kixiQu 5y ago
    Some people are willing to be meticulous about references even when they're Less Good Than One Might Wish at picking names or explaining things.
  - tjoff 5y ago
    You don't think that "the author thought that this function would return X, but I got Y" is useful?
    - kadoban 5y ago
      Only for archeological, and maybe sometimes psychological investigations of code.
      - tjoff 5y ago
        That line of reasoning doesn't make any sense to me. If the author / last person who touched the code misunderstood it then there is a 100% chance there is a bug here. Knowing that off the bat is quite helpful. And it also tells something about the code quality if it is a common occurrence.
        smitty1e 5y ago
        Could be an indicator to look up the file in git log. Which need would send me back to pypi to look at other prior art, if possible.
- pvillano 5y ago
  type hints are documentation, and machine readable documentation to boot!
np_tedious 5y ago
> I'm not even using mypy often, if ever. Hopefully your CI does?
- linsomniac 5y ago
  Not yet, but that might be coming. I have one personal project set up to run mypy as a pre-commit, but I'm not (quite) ready to force that on my coworkers.
- Spivak 5y ago
  It's not really as necessary as you think -- making mypy/pyright pass your CI ends up being a lot of busy work to make the type checker happy when, to me, all the value is realized when it's used as a development aid. If your test suite passes that's honestly more than good enough.
  - icedchai 5y ago
    You have the right attitude. I have worked with delusional individuals who one day "soon" expect to mypy check their entire several hundred thousand line legacy code base. This is supposed to be a boon to developer productivity. I hope it outweighs what was lost getting to this point.
gkhartman 5y ago
I use them for the same reason. I've started sprinkling them into projects where I can. Other devs on the team seem to like seeing them, but have higher inertia when it comes to writing them.
mountainriver 5y ago
Not typing is kinda a crazy way to write programs when you think about it. It can be beneficial in certain niche use cases like data science where code is always terrible. For everything else, types are a huge boon for the developer and everyone consuming their work
- waitlist 5y ago
  I think data science is a perfect example in favor of types -- the code is often terrible because of the lack of typing. Pandas has notoriously poor developer ergonomics, and I recall painfully poring over type errors across the board -- lists, dataframes, numpy arrays, etc. are all iterables, so they can be interchanged in some contexts, but not in others. Had I had MyPy back when I was working in data science, I would've saved countless hours and headaches.
  - bayesian_horse 5y ago
    What Pandas does is notoriously hard to fit into a compile-time type system. Certainly too hard to go into the brains of scientists who didn't grow up coding. No, the code in data science isn't bad because of the lack of typing. The code is "bad" mostly because those writing it are relatively fresh from starting to program. Also there is more pressure to make things possible, often just to run it once, and neglect repeatability or scaling to larger code bases. Different emphasis. That doesn't mean an experienced full stack developer would do Data Science better, because he might lack a lot of skills that matter more in that domain.
    - arinlen 5y ago
      > What Pandas does is notoriously hard to fit into a compile-time type system. Certainly too hard to go into the brains of scientists who didn't grow up coding. I'm not sure if that's true. Doesn't Pandas handle ETL and some anaysis? There is nothing inherent to ETL that makes it a hard problem with compiled languages. In your opinion, what does Pandas do that's hard to do with compile-time languages?
bageljr 5y ago
Actually depending on the LSP, you are using a type checker since Pyright is its own type checker and Pylsp has a mypy plugin
kgbcia 5y ago
same, started using Objects and Classes more to get type hint support
yowlingcat 5y ago
Have you (or anyone else on this thread) used retype or MonkeyType? We have a codebase right now that's mostly lacking type hints. But, now that we have added automatic flaking into our build (and pre-commit hooks), I'd like to get some more mileage out of that toolchain we just invested into, but it would be a hassle to go back and add type hinting to everything. What I'd like to do is integrate something into our pre-commit hooks.

totony 5y ago

>My editor now has a fairly deep understanding of my code, and can tell me of all sorts of surprising errors I'm making before I run the code. I agree this is useful, but to me the most useful feature of types are the self-documentation. It's crazy the difference between a non-typed library with shitty documentation vs a typed library with shitty documentation.

kadoban 5y ago
The types on stitty-documented code often do depend on the types actually being checked though. Otherwise you need to author to be diligent in their types, but if they're bad in their other docs, that seems unlikely.
- kixiQu 5y ago
  Some people are willing to be meticulous about references even when they're Less Good Than One Might Wish at picking names or explaining things.
- tjoff 5y ago
  You don't think that "the author thought that this function would return X, but I got Y" is useful?
  - kadoban 5y ago
    Only for archeological, and maybe sometimes psychological investigations of code.
    - tjoff 5y ago
      That line of reasoning doesn't make any sense to me. If the author / last person who touched the code misunderstood it then there is a 100% chance there is a bug here. Knowing that off the bat is quite helpful. And it also tells something about the code quality if it is a common occurrence.
      - smitty1e 5y ago
        Could be an indicator to look up the file in git log. Which need would send me back to pypi to look at other prior art, if possible.
pvillano 5y ago
type hints are documentation, and machine readable documentation to boot!

np_tedious 5y ago

> I'm not even using mypy often, if ever. Hopefully your CI does?

linsomniac 5y ago
Not yet, but that might be coming. I have one personal project set up to run mypy as a pre-commit, but I'm not (quite) ready to force that on my coworkers.
Spivak 5y ago
It's not really as necessary as you think -- making mypy/pyright pass your CI ends up being a lot of busy work to make the type checker happy when, to me, all the value is realized when it's used as a development aid. If your test suite passes that's honestly more than good enough.
- icedchai 5y ago
  You have the right attitude. I have worked with delusional individuals who one day "soon" expect to mypy check their entire several hundred thousand line legacy code base. This is supposed to be a boon to developer productivity. I hope it outweighs what was lost getting to this point.

gkhartman 5y ago

I use them for the same reason. I've started sprinkling them into projects where I can. Other devs on the team seem to like seeing them, but have higher inertia when it comes to writing them.

mountainriver 5y ago

Not typing is kinda a crazy way to write programs when you think about it. It can be beneficial in certain niche use cases like data science where code is always terrible. For everything else, types are a huge boon for the developer and everyone consuming their work

waitlist 5y ago
I think data science is a perfect example in favor of types -- the code is often terrible because of the lack of typing. Pandas has notoriously poor developer ergonomics, and I recall painfully poring over type errors across the board -- lists, dataframes, numpy arrays, etc. are all iterables, so they can be interchanged in some contexts, but not in others. Had I had MyPy back when I was working in data science, I would've saved countless hours and headaches.
- bayesian_horse 5y ago
  What Pandas does is notoriously hard to fit into a compile-time type system. Certainly too hard to go into the brains of scientists who didn't grow up coding. No, the code in data science isn't bad because of the lack of typing. The code is "bad" mostly because those writing it are relatively fresh from starting to program. Also there is more pressure to make things possible, often just to run it once, and neglect repeatability or scaling to larger code bases. Different emphasis. That doesn't mean an experienced full stack developer would do Data Science better, because he might lack a lot of skills that matter more in that domain.
  - arinlen 5y ago
    > What Pandas does is notoriously hard to fit into a compile-time type system. Certainly too hard to go into the brains of scientists who didn't grow up coding. I'm not sure if that's true. Doesn't Pandas handle ETL and some anaysis? There is nothing inherent to ETL that makes it a hard problem with compiled languages. In your opinion, what does Pandas do that's hard to do with compile-time languages?

bageljr 5y ago

Actually depending on the LSP, you are using a type checker since Pyright is its own type checker and Pylsp has a mypy plugin

kgbcia 5y ago

same, started using Objects and Classes more to get type hint support

yowlingcat 5y ago

Have you (or anyone else on this thread) used retype or MonkeyType? We have a codebase right now that's mostly lacking type hints. But, now that we have added automatic flaking into our build (and pre-commit hooks), I'd like to get some more mileage out of that toolchain we just invested into, but it would be a hassle to go back and add type hinting to everything. What I'd like to do is integrate something into our pre-commit hooks.