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> Put simply: enabling mypy + no-any gives you all the same static guarantees (and arguably more) that java does, so in what way isn't it statically typed? The

> Put simply: enabling mypy + no-any gives you all the same static guarantees (and arguably more) that java does, so in what way isn't it statically typed? The original question was about Python the language, not Python the ecosystem. At no point is it ever likely to be correct to say "Python is statically typed"; it will only be possible to say "this specific Python code can be statically typed, if you run the static type checker". This is a fundamental difference between optional static typing in Python versus a natively statically typed language. Because you can run the Python code without running the static type checks, which you cannot do in, say, Java. Because of this distinction, it is never a genuine concern of a developer in Java or another statically typed language whether third-party libraries will be properly typed. There do not exist libraries without valid static types. You can't install something from Maven or what-have-you that won't type-check. But you can do this in Python. You can install something via pip and there is no guarantee it will come with good type annotations for your type-checking tool to use, because the type checker is not part of the language proper. It's not required. So Python code exists in the real world that cannot be used with the same assumptions as you can use code in the Java ecosystem. And this is fine, by and large, because Python wasn't meant to be typed. There's nothing wrong with using code like this, nor is there anything wrong with writing code like this. You may not wish to do so personally, which is fine, but I don't think there will ever be an expectation made by the Python language proper of all Python developers to annotate their code. Python will always work without explicit types. My point in all of this is that your original argument that "[whether there are concerns about third-party libraries having valid type annotations] is true in any type system" does not hold in the real world, because you simply won't have untyped libraries in a statically typed language's ecosystem like you will in Python. Perhaps you didn't realize that this was the point being made, but in any case you went off on a very semantic tangent that had no real bearing on the conversation at hand: the use of type annotations in practice.

joshuamorton 6y ago
> The original question was about Python the language, not Python the ecosystem. Python doesn't have a spec, so the argument that the language doesn't support static typing is dubious at best, since a static type checker is maintained by the language itself. If I alias python to `mypy $0 && python $0` or whatnot, is it no longer python? It's certainly statically typed. > Because of this distinction, it is never a genuine concern of a developer in Java or another statically typed language whether third-party libraries will be properly typed. There do not exist libraries without valid static types. You can't install something from Maven or what-have-you that won't type-check. Is this enforced by the language, or is this just an aspect of the ecosystem? "Maven-packages must typecheck" is enforced by the spec? > But you can do this in Python. You can install something via pip and there is no guarantee it will come with good type annotations for your type-checking tool to use, because the type checker is not part of the language proper. It's not required. Are you saying that there is a guarantee in Java that the types need to be "good"? I'm not even clear that maven (which again isn't part of the java language) requires that uploads compile, much less that the type declarations be "good", whatever that means. Which all returns to my central point: you trust the java ecosystem more that the python ecosystem to have "good" type declarations. There is nothing implicit in the type systems of those languages that enforces that one or the other have better or worse type annotations. Your argument relies on conflating use in practice with theoretical guarantees, I'm just pointing that out. If you want to say that your experience is that python has less reliable types than java, then sure, that's probably true. But the type systems available in those languages are functionally equivalent. The use, however, differs.
- DonaldPShimoda 6y ago
  It really feels like your entire contribution to this discussion amounts to "but what if we ignore the point being made and instead just focus on very strict semantic interpretations of the language other people in the conversation are using". I feel like you have not really engaged with my actual points and instead have focused on finding details to complain about in service of appearing to make a point, which effectively derails the true conversation. I find this incredibly frustrating, and I have no interest in continuing. I would politely suggest you consider whether this is a common issue you have with people or whether it's just me (certainly a possibility, I admit). If this happens to you often, you may want to try alternative approaches to broaching your points if you'd like better engagement. I think most people don't enjoy when their main points are continually ignored in favor of bringing up other minutiae to prove that they're wrong or something. Regardless, cheers.

joshuamorton 6y ago

> The original question was about Python the language, not Python the ecosystem. Python doesn't have a spec, so the argument that the language doesn't support static typing is dubious at best, since a static type checker is maintained by the language itself. If I alias python to `mypy $0 && python $0` or whatnot, is it no longer python? It's certainly statically typed. > Because of this distinction, it is never a genuine concern of a developer in Java or another statically typed language whether third-party libraries will be properly typed. There do not exist libraries without valid static types. You can't install something from Maven or what-have-you that won't type-check. Is this enforced by the language, or is this just an aspect of the ecosystem? "Maven-packages must typecheck" is enforced by the spec? > But you can do this in Python. You can install something via pip and there is no guarantee it will come with good type annotations for your type-checking tool to use, because the type checker is not part of the language proper. It's not required. Are you saying that there is a guarantee in Java that the types need to be "good"? I'm not even clear that maven (which again isn't part of the java language) requires that uploads compile, much less that the type declarations be "good", whatever that means. Which all returns to my central point: you trust the java ecosystem more that the python ecosystem to have "good" type declarations. There is nothing implicit in the type systems of those languages that enforces that one or the other have better or worse type annotations. Your argument relies on conflating use in practice with theoretical guarantees, I'm just pointing that out. If you want to say that your experience is that python has less reliable types than java, then sure, that's probably true. But the type systems available in those languages are functionally equivalent. The use, however, differs.

DonaldPShimoda 6y ago
It really feels like your entire contribution to this discussion amounts to "but what if we ignore the point being made and instead just focus on very strict semantic interpretations of the language other people in the conversation are using". I feel like you have not really engaged with my actual points and instead have focused on finding details to complain about in service of appearing to make a point, which effectively derails the true conversation. I find this incredibly frustrating, and I have no interest in continuing. I would politely suggest you consider whether this is a common issue you have with people or whether it's just me (certainly a possibility, I admit). If this happens to you often, you may want to try alternative approaches to broaching your points if you'd like better engagement. I think most people don't enjoy when their main points are continually ignored in favor of bringing up other minutiae to prove that they're wrong or something. Regardless, cheers.