8 ms·

Fully agree with this. Type hinting (not checking) is idiomatic to Python. MyPy is a great way to enforce checking. It's great to have the option to use the hin

Fully agree with this. Type hinting (not checking) is idiomatic to Python. MyPy is a great way to enforce checking. It's great to have the option to use the hints for intellisense only.

mejutoco 4y ago
My favourite way to enforce types in python is to use typeguard‘s typechecked decorator. It is checked at runtime but it can be added gradually. https://pypi.org/project/typeguard/ https://pypi.org/project/typeguard/
throwaway81523 4y ago
I've found that even when I write code intended to be statically checked from the beginning, mypy often misses stuff. I was enthusiastic about mypy at first and I still use it, but I'm not sure at this point that it is worth it.
- the_af 4y ago
  Same here. And I come from (and am a fan of) statically typed languages. The type hinting story for Python seems confusing and not completely useful to me.
  - seti0Cha 4y ago
    I just started using type hinting in Python and I love it. Maybe it's your tooling? I'm using neovim with LSP and pyright and the experience is very much like writing code in a Java IDE. As I code, it informs me where there are mistakes or pieces of code that need to be updated, catches typos, reminds me about forgotten imports, etc. It makes refactoring way easier because as you change signatures or object types it flags all the places in your code that need to be updated. Seems like a real game changer to me.
    - the_af 4y ago
      I want automated type checking outside the IDE. I want something that will catch other programmer's mistakes, not just mine. Without enforcing a specific IDE.
      - seti0Cha 4y ago
        LSP support exists for many editors so you are not tied to a specific IDE. It can catch other programmers mistakes if you run it against their code. It doesn't turn Python into a statically typed language, but it's a lot better than nothing.
        the_af 4y ago
        Sorry, I wasn't clear. I don't want to mess with each individual developers IDE or setup. I want to enforce type checking at the same place we also run mandatory tests: in the automated build pipeline (think CI/CD).
    - throwaway81523 4y ago
      No it's not the tooling, unless by tooling you mean mypy. The issue is that you can write code with type errors that mypy doesn't catch. In what I usually think of as static typing, that would be impossible: type errors are simply not allowed, even if that means the compiler rejects some otherwise-valid code. I think mypy has to let some potential errors through because otherwise it would spew 1000's of spurious error messages on perfectly good, unannotated legacy code. Something similar happens with the Erlang dialyzer. The same thing applies to tools like Coverity, that aim to find potential bugs in legacy C code. You could instead imagine a version of mypy that makes no concessions at all to legacy code, and insists that your code be 100% free of type errors, even if that means that some older constructs and styles no longer work. Would that be a good thing? Probably not: we have Haskell for that. Mypy's leaking errors is probably a practical necessity in retrospect. But, I wasn't expecting the leakage, so it surprised and disappointed me when I encountered it. I had thought I was getting something more like Haskell. Mypy still has attractions, but it's less great than I had hoped.
- noitpmeder 4y ago
  I think this is only going to happen in reality if you're doing funky type hacks in the first place. Mypy definitely has rough edges, but it works perfectly in 95% of every codebase I've seen. Type hints (with mypy) aren't going to save you from becomming a bad programmer. But they _do_ help you become a better one!
the_af 4y ago
Honest question: what's the point of type hinting without type checking? I must be mistaken, but I always thought "type hinting" was a synonym of "optional type annotations". But if you're not using those annotations for actual type checking at some point, what are they good for?
- xarope 4y ago
  as a reminder for yourself/others who need to read/maintain your code? (I am often reminded of my perl days, where something I thought idiomatic 3 days ago, is now completely incomprehensible when I just want to make a minor change)
  - the_af 4y ago
    So is it simply a standardized comment then? I will have a really bad time convincing my team mates, if that's the case. It's especially bad because, like any comment, it can say one thing but the code may do something different (actually happened to me).
    - zokier 4y ago
      yes, and yes. and they are still useful.
    - rglullis 4y ago
      You can have mypy doing the type checking. Just put it on your CI pipeline alongside your tests.
      - the_af 4y ago
        I know because I tried setting it up. It's slow, requires too much babysitting, and fails to catch cases. In my experience, it just doesn't work cleanly out of the box like in true statically typed languages, and so I get pushback from my coworkers, who simply can't see the point. And I can't blame them.
mirashii 4y ago
I actually find that mypy is pretty weak and lacking, even within the python ecosystem. pyright seems to do a much better job at the type checking portion of things.

Fully agree with this. Type hinting (not checking) is idiomatic to Python. MyPy is a great way to enforce checking. It's great to have the option to use the hints for intellisense only.

mejutoco 4y ago

My favourite way to enforce types in python is to use typeguard‘s typechecked decorator. It is checked at runtime but it can be added gradually. https://pypi.org/project/typeguard/ https://pypi.org/project/typeguard/

throwaway81523 4y ago

I've found that even when I write code intended to be statically checked from the beginning, mypy often misses stuff. I was enthusiastic about mypy at first and I still use it, but I'm not sure at this point that it is worth it.

the_af 4y ago
Same here. And I come from (and am a fan of) statically typed languages. The type hinting story for Python seems confusing and not completely useful to me.
- seti0Cha 4y ago
  I just started using type hinting in Python and I love it. Maybe it's your tooling? I'm using neovim with LSP and pyright and the experience is very much like writing code in a Java IDE. As I code, it informs me where there are mistakes or pieces of code that need to be updated, catches typos, reminds me about forgotten imports, etc. It makes refactoring way easier because as you change signatures or object types it flags all the places in your code that need to be updated. Seems like a real game changer to me.
  - the_af 4y ago
    I want automated type checking outside the IDE. I want something that will catch other programmer's mistakes, not just mine. Without enforcing a specific IDE.
    - seti0Cha 4y ago
      LSP support exists for many editors so you are not tied to a specific IDE. It can catch other programmers mistakes if you run it against their code. It doesn't turn Python into a statically typed language, but it's a lot better than nothing.
      - the_af 4y ago
        Sorry, I wasn't clear. I don't want to mess with each individual developers IDE or setup. I want to enforce type checking at the same place we also run mandatory tests: in the automated build pipeline (think CI/CD).
  - throwaway81523 4y ago
    No it's not the tooling, unless by tooling you mean mypy. The issue is that you can write code with type errors that mypy doesn't catch. In what I usually think of as static typing, that would be impossible: type errors are simply not allowed, even if that means the compiler rejects some otherwise-valid code. I think mypy has to let some potential errors through because otherwise it would spew 1000's of spurious error messages on perfectly good, unannotated legacy code. Something similar happens with the Erlang dialyzer. The same thing applies to tools like Coverity, that aim to find potential bugs in legacy C code. You could instead imagine a version of mypy that makes no concessions at all to legacy code, and insists that your code be 100% free of type errors, even if that means that some older constructs and styles no longer work. Would that be a good thing? Probably not: we have Haskell for that. Mypy's leaking errors is probably a practical necessity in retrospect. But, I wasn't expecting the leakage, so it surprised and disappointed me when I encountered it. I had thought I was getting something more like Haskell. Mypy still has attractions, but it's less great than I had hoped.
noitpmeder 4y ago
I think this is only going to happen in reality if you're doing funky type hacks in the first place. Mypy definitely has rough edges, but it works perfectly in 95% of every codebase I've seen. Type hints (with mypy) aren't going to save you from becomming a bad programmer. But they _do_ help you become a better one!

the_af 4y ago

Honest question: what's the point of type hinting without type checking? I must be mistaken, but I always thought "type hinting" was a synonym of "optional type annotations". But if you're not using those annotations for actual type checking at some point, what are they good for?

xarope 4y ago
as a reminder for yourself/others who need to read/maintain your code? (I am often reminded of my perl days, where something I thought idiomatic 3 days ago, is now completely incomprehensible when I just want to make a minor change)
- the_af 4y ago
  So is it simply a standardized comment then? I will have a really bad time convincing my team mates, if that's the case. It's especially bad because, like any comment, it can say one thing but the code may do something different (actually happened to me).
  - zokier 4y ago
    yes, and yes. and they are still useful.
  - rglullis 4y ago
    You can have mypy doing the type checking. Just put it on your CI pipeline alongside your tests.
    - the_af 4y ago
      I know because I tried setting it up. It's slow, requires too much babysitting, and fails to catch cases. In my experience, it just doesn't work cleanly out of the box like in true statically typed languages, and so I get pushback from my coworkers, who simply can't see the point. And I can't blame them.

mirashii 4y ago

I actually find that mypy is pretty weak and lacking, even within the python ecosystem. pyright seems to do a much better job at the type checking portion of things.