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Comment by alanfranzoni | Hacker News Reader

Bah. If you want a statically typed language, get a statically typed language.

What's a type hint for if, after that, the user can actually pass a different type?

A type checker for Python can say: "pass", "reject" or "I don't know".

Statically typed languages (1) introduce limitations so that type checking is decidable (no incertitude), or (2) or treat "don't know" as "reject", because the runtime has practically no knowledge of type. This is not the case in Python, so you don't have to check everything. That does not mean you shouldn't check anything.

So there are still benefits in Python to have type in order to "reject" code that is undoubtedly going to produce type errors at runtime (or maybe to optimize things). In case of uncertainty, you know the runtime is going to catch errors anyway (including type errors).

For structurally typed languages you really want something like C++'s concepts so you can talk about `Iterable[str]` rather than forcing it to `List[str]`. Is this possible with Python's type annotations?

I don't know exactly for Python. I would expect mixin class to be used for this. Also, maybe Python will allow you to define union types: e.g. X is either a "foo", a "bar" or a "zot" (all of them duck types the same implicit interface).

It's kind of hard because you really want to be able to use generator functions as well. Maybe that just can't be properly described Python. It would be shame to lose out on passing a generator because somebody has used `List[int]` inside a function that really takes an iterable.

And that's why it's bad. Let's throw something useful (duck typing) out of the window to please the Java people

I'm sincerely disgusted

> Let's throw something useful (duck typing)

Not sure why you say this is throwing away duck typing, you just don't add a type hint and you continue working as usual.

> I'm sincerely disgusted

I can sympathize, most of the time when there is a talk about Lisp there is a guy who comes just to say "dynamic typing is bad", etc. Well, even though there are definitely static analyzers for Lisp (see https://news.ycombinator.com/item?id=12216701), the language is still the same and doesn't prevent anyone from using dynamic features. People who really want statically typed programs won't touch Python anyway so I don't think you have much to worry.

Yup. There is a Generic type which uses duck typing and has an `Iterable` subclass for classes implementing __iter__() (https://docs.python.org/3/library/typing.html#typing.Generic). It has been pointed out though that `str` counts as an instance of Iterable[str], so there is a possibility for some amusing issues to arise from this.

If I am programming in Python, I want nothing wrong to happen because I passed the "wrong type". That's the same argument as "don't use isinstance". It's not Pythonic. If you want a dynamically typed language, you don't check types. Period.

Type hinting would be ok for documentation only. But then, a comment is fine and introduces less clutter.

Well, maybe "reject" was too strong a word.

The warnings that are emitted by SBCL (Lisp implementation) are produced when two types don't intersect at all, something like "len(3)". There is no warning when types overlap. And even if the warning is issued, the code is still compiled and can run.

IDE code completion and linting, which is admittedly an area where Python sucks.

But I'm inclined to agree. It's a little too to add static typing to Python. You're just going to end up with something far worse than a language that was designed with it in mind, like Ceylon or Go.

Python is a language where I simply don't miss code completion.

Why not? Code completion is definitely useful in Python (when it works, which is rarely). It saves time looking up documentation.

I find I can keep most things I currently need in my head with Python.

Which is nice as some IDEs tend to offer code completion popups OVER the line I'm typing which is very annoying and breaks my thought process.

Also, for _me_, not using code completion helps me think more about what I'm actually doing and not code so much on autopilot. I actually write much better, succinct code without completion.

YMMV

Sounds very like an excuse to me.

> Bah. If you want a statically typed language, get a statically typed language.

Which statically typed scripting language would you suggest instead of Python?

What do you mean by "scripting language"? That's an old terminology which is lacking a clear sense nowadays.

Would you like something that you can embed? Something that has an interpreter for?

> What do you mean by "scripting language"? That's an old terminology which is lacking a clear sense nowadays.

https://en.wikipedia.org/wiki/Scripting_language

> Would you like something that you can embed? Something that has an interpreter for?

I asked about your personal preference regarding a statically typed alternative to Python. Can you propose one?

I'm not the person that you responded to, but C# has a nice scripting API and repl.

for documentation

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