From this example:
lazy from typing import Iterator
def stream_events(...) -> Iterator[str]:
while True:
yield blocking_get_event(...)
events = stream_events(...)
for event in events:
consume(event)
> When an AttributeError on a builtin type has no close match via Levenshtein distance, the error message now checks a static table of common method names from other languages (JavaScript, Java, Ruby, C#) and suggests the Python equivalent
Oh, that is such a nice thing.
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Now I'm wishing for a single cross-language library, that I can somehow inject into every compiler/runtime/checker to get this, but with a single source of truth and across a wide range of languages. I hit this damn issue all the time, writing code in one language for another, would truly be a bliss to have that problem solved once and for all.
What benefit does the lazy import have here - if we use the value in a type hint at module scope anyway? Would that require Deferred evaluation of annotations -- which I don't think are enabled by default?
Type annotations are lazily evaluated by moving them behind a special annotations scope as of 3.14:
https://peps.python.org/pep-0649/
https://docs.python.org/3/reference/compound_stmts.html#anno...
With 3.15, using lazy typing imports is more or less an alternative to putting such imports behind an "if TYPE_CHECKING" guard.
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Yes, 3.15+
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Python is such a weird language. Lazy imports are a bandaid for AI code base monstrosities with 1000 imports (1% of which are probably Shai Hulud now).
And now even type imports are apparently so slow that you have to disable them if unused during the normal untyped execution.
If Instagram or others wants a professional language, they should switch to Go or PHP instead of shoehorning strange features into a language that wasn't built for their use cases.
> Python is such a weird language. Lazy imports are a bandaid for AI code base monstrosities with 1000 imports
Just because you don’t like a feature doesn’t mean it’s because of AI and bad code.
I think this is just a natural consequence of an easy-to-use package system. The exact same story as with node. If you don't want lots of imports, don't make it so damn easy to pile them into projects. I'm frankly surprised we still see so few supply chain attacks, even though they picked up their cadence dramatically.
This seems a lot more due to an import running arbitrary code because stuff can happen in the top-level of a module rather than only happening in functions. From what I can tell, it seems pretty common for dynamically typed languages and pretty much entirely absent from statically typed ones, which tend to have a main function that everything else happens inside transitively. I guess this makes it easy if what you're writing is something that runs with no dependencies, but it's a pretty terrible experience as soon as you try to introduce the concept of a library.
> it seems pretty common for dynamically typed languages and pretty much entirely absent from statically typed ones
Counter-example is Go and init() function.
Interesting, I had no idea that existed! I still think there's a a difference between "here's a hook you can use to run stuff earlier" and "importing any module is fundamentally the same as running it as a script unless the module happens to use a special conditional to wrap stuff inside of" though (and I say this as someone who doesn't go out of his way to defend Go design decisions)
Also C++/Java static initialization, C# static constructors, or Rust global variable initialization, ...
Most languages have this feature Afaik
What would your alternative look like?
Too much syntactic sugar causes cancer of the semicolon.
True, but this is yet another code path that isn't exercised until specific conditions happen. That means even more latent application behaviour can go undetected by unit testing and security profiling until the moon is in the right phase, which is a boon for submarine attacks.
Empirically, I have used the current accepted way to do lazy imports (import statement inside a function) before AI coding was even a mainstream thing, for personal code that sometimes needs a heavy import and sometimes doesn’t.
The lazy statement would be an improvement as it allows one to see all the imports at the top where you expect them to be.
As a now deleted comment pointed out, lazy imports had been requested forever. They were rejected forever and were accepted just when BigCorps wanted them.
Python-dev now is paid to shore up the failed Instagram stack.
It was accepted just as multiple large corporations with competent teams of internal tool departments ended up forking the interpreter to support lazy imports and demonstrated empirically that the idea has merit.
I too am outraged that a product would prioritize its biggest users.
Is the biggest user larger than the combined set of individual users who had asked for (or would benefit from) the same thing? I honestly don't know, but I don't think that things are always as simple as you're implying in a world where we have the collective action problem.
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On most unix-likes all "imports" via shared libraries (e.g. in C / C++) are lazy by default.
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But also great for speed. Larger libraries can take a measurable amount of time to import (even if they have no transitive dependencies). If only some of your code paths actually need the large library then it makes sense to import it lazily. Without lazy you have to do it conditionally which can lead to the imports happening in strange places rather than all being listed out at the top of the file.