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It seems to me like Python needs to get Typescript's capabilities (if Python wants to go further this way of course). It solves all these problems very well, an

by dtech 4y ago

It seems to me like Python needs to get Typescript's capabilities (if Python wants to go further this way of course). It solves all these problems very well, and has no problem with 2 and most of the author's objections.

ledauphin 4y ago
Typescript does absolutely fantastic type inference, which mypy definitely does not. I think that's a huge advantage for Typescript over mypy, and it's really foundational to the value it provides. However, even in Typescript it is nontrivial to _annotate_ these complex types, and in most cases it's still possible to do in Python - you just need to commit to using something like dataclasses rather than pretending that what you have is a `dict`. Basically, to get the most out of static typing in the world of Python, you do have to write more boilerplate than you would in Typescript, and in particular you need to avoid dicts and prefer various sorts of class-based data containers (again, dataclasses, attrs, namedtuples, etc).
- eyelidlessness 4y ago
  > However, even in Typescript it is nontrivial to _annotate_ these complex types The only one which stands out to me as non-trivial in TypeScript is thrown exceptions… and even then only because you can only type them in a catch clause, and only with unknown, and they’re invisible to callers. But then this is why people who would care for checked exceptions quite reasonably just use something like a Result type. But I agree with your conclusion completely, and it’s basically the same one I came to reading the post. I was curious about how the current state of things compares to TS, as I may soon have a foray back into Python soon, and would be delighted to bring some static types into the mix. Pretty much as I expected, it’ll probably be more effort/less valuable than TS, but more valuable to me than to the author.
  - strogonoff 4y ago
    I had to come back to Python after working with TypeScript for a while. After going from Python 2.x to TypeScript and being very impressed with static typing, I didn’t want to go back to untyped so I had to get up to speed with the ecosystem. My findings: — Consider using Pydantic (either its drop-in dataclasses replacement, or its models). It has issues and documentation is lacking in places, but in many use cases it’s a boon when it comes to being confident about data you read and/or pass around. — Don’t use TypedDict if you foresee needing anything like optional keys, especially with defaults. I went with TypedDict and it came back to bite me later (though was relatively easy to refactor). — Keep an eye on https://pypi.org/project/typing-extensions/ https://pypi.org/project/typing-extensions/, it has some useful utility types. I wish I knew about this package a couple of months back. — If you use VS Code (which I started after switching to TS), there’re some shenanigans to be aware of. Unlike TypeScript’s elegant approach where you’re in control of installing typing versions, VS Code’s official Python extension will force-install unvetted third-party typings, not caring if they don’t match library versions in your use and not allowing to opt out. In later versions you can unset mypy in Python extension settings, and use a separate Mypy extension that doesn’t do this behind your back and doesn’t send you deep into some rando’s typings when you hit F12 to jump to definition. — That aside, VS Code can provide development experience is not that far from TypeScript. You can keep a virtualenv nearby and select its Python bin as interpreter in your workspace, giving Mypy access to dependencies (and if VS Code’s interpreter selection GUI resolves symlinks, you can enter interpreter path by hand so that it doesn‘t). — Sphinx documentation is good at picking up typing hints and works reasonably well with Pydantic’s models, too.
    - eyelidlessness 4y ago
      Thank you for so much detailed advice! I’m sure this will be valuable to reference as I dive in
- oefrha 4y ago
  You can type Python dicts, see typing.TypedDict. It’s still lacking though, totality is all or nothing until py311, that is to say, TypedDict’s are either Required<T> or Partial<T> in TypeScript parlance. And you don’t get Pick<T>, Omit<T>, etc.
edgyquant 4y ago
The ability to slowly add typed code to an existing database has been a lifesaver. I always hated JS because of callback hell (and the notions around its community) but since I started working with typescript my mind has been changed. I love it

by dtech 4y ago

ledauphin 4y ago

Typescript does absolutely fantastic type inference, which mypy definitely does not. I think that's a huge advantage for Typescript over mypy, and it's really foundational to the value it provides. However, even in Typescript it is nontrivial to _annotate_ these complex types, and in most cases it's still possible to do in Python - you just need to commit to using something like dataclasses rather than pretending that what you have is a `dict`. Basically, to get the most out of static typing in the world of Python, you do have to write more boilerplate than you would in Typescript, and in particular you need to avoid dicts and prefer various sorts of class-based data containers (again, dataclasses, attrs, namedtuples, etc).

eyelidlessness 4y ago
> However, even in Typescript it is nontrivial to _annotate_ these complex types The only one which stands out to me as non-trivial in TypeScript is thrown exceptions… and even then only because you can only type them in a catch clause, and only with unknown, and they’re invisible to callers. But then this is why people who would care for checked exceptions quite reasonably just use something like a Result type. But I agree with your conclusion completely, and it’s basically the same one I came to reading the post. I was curious about how the current state of things compares to TS, as I may soon have a foray back into Python soon, and would be delighted to bring some static types into the mix. Pretty much as I expected, it’ll probably be more effort/less valuable than TS, but more valuable to me than to the author.
- strogonoff 4y ago
  I had to come back to Python after working with TypeScript for a while. After going from Python 2.x to TypeScript and being very impressed with static typing, I didn’t want to go back to untyped so I had to get up to speed with the ecosystem. My findings: — Consider using Pydantic (either its drop-in dataclasses replacement, or its models). It has issues and documentation is lacking in places, but in many use cases it’s a boon when it comes to being confident about data you read and/or pass around. — Don’t use TypedDict if you foresee needing anything like optional keys, especially with defaults. I went with TypedDict and it came back to bite me later (though was relatively easy to refactor). — Keep an eye on https://pypi.org/project/typing-extensions/ https://pypi.org/project/typing-extensions/, it has some useful utility types. I wish I knew about this package a couple of months back. — If you use VS Code (which I started after switching to TS), there’re some shenanigans to be aware of. Unlike TypeScript’s elegant approach where you’re in control of installing typing versions, VS Code’s official Python extension will force-install unvetted third-party typings, not caring if they don’t match library versions in your use and not allowing to opt out. In later versions you can unset mypy in Python extension settings, and use a separate Mypy extension that doesn’t do this behind your back and doesn’t send you deep into some rando’s typings when you hit F12 to jump to definition. — That aside, VS Code can provide development experience is not that far from TypeScript. You can keep a virtualenv nearby and select its Python bin as interpreter in your workspace, giving Mypy access to dependencies (and if VS Code’s interpreter selection GUI resolves symlinks, you can enter interpreter path by hand so that it doesn‘t). — Sphinx documentation is good at picking up typing hints and works reasonably well with Pydantic’s models, too.
  - eyelidlessness 4y ago
    Thank you for so much detailed advice! I’m sure this will be valuable to reference as I dive in
oefrha 4y ago
You can type Python dicts, see typing.TypedDict. It’s still lacking though, totality is all or nothing until py311, that is to say, TypedDict’s are either Required<T> or Partial<T> in TypeScript parlance. And you don’t get Pick<T>, Omit<T>, etc.

edgyquant 4y ago

The ability to slowly add typed code to an existing database has been a lifesaver. I always hated JS because of callback hell (and the notions around its community) but since I started working with typescript my mind has been changed. I love it