3 ms·

> But I guess it's going to be 2 params from now on. >> So, if you discover that a code path you previously thought was pure actually does need to perform IO,

> But I guess it's going to be 2 params from now on. >> So, if you discover that a code path you previously thought was pure actually does need to perform IO, then you don't need to apply some nasty viral change; you just grab `my_thing.io

camgunz 1y ago
Python, for example, will let you call async functions inside non-async functions, you just have to set up the event loop yourself. This isn't conceptually different than the Io thing here.
- throwawaymaths 1y ago
  except you cant "pass the same event loop in multiple locations". its also not an easy lift. the zig std will provide a few standard implementations which would be trivial to drop in.
  - camgunz 1y ago
    I thought it was the exact same; an event loop in Python is just whatever Io is in Zig, make it a param, get it from an import and a lookup (`import asyncio; loop = asyncio.get_running_loop()`). I might be misunderstanding what you're saying though.
    - deleted 1y ago
      [deleted]
    - throwawaymaths 1y ago
      hm maybe. i guess ive only used python in situations where it injects it into amain so i could have been confused. i thought python async was a wrapper around generators, and so the mechanism cant be instantiated in multiple places. i stand corrected.
      - camgunz 1y ago
        Oh no you're right it's a pain in the ass and weird. But I think it's the way because there's no good reason to have more than one event loop. Also... maybe it started out as generator wrappers? I think I read something that said that.
        Spivak 1y ago
        > no good reason to have more than one event loop Per thread—once you start working in multiple threads you have the choice to have one global event loop, which comes at the cost of all async code being effectively serialized as far as threads are concerned*, or one event loop per thread. * Which can be fine if your program is mostly not async but you have that one stubborn library. Yay async virality.
        camgunz 1y ago
        I can't say there's no good reason to have per thread event loops, but I think I can say if you do know of one you're suffering a terrible curse. I can only imagine the constraints that would force me to do this.
        Spivak 1y ago
        Because you have a main application running a web server and a daemon worker thread performing potentially long running tasks that use async libraries and you don't want to block the responsiveness of your web server. It's really not that bad, at least in Python.
        camgunz 1y ago
        Well, here we go I guess. Why can't you just use FastAPI? Or Tornado? Isn't there also an async Flask? Isn't Django also async now? What minor god have you angered to be chained to a non-async framework?
        1y ago
- gpderetta 1y ago
  But the asyncio event loop is not reentrant, so your faux sync functions cannot be safely called from other async functions. It is an extremely leaky abstraction. This is not a theoretical possibility, I stumbled on the issue 15 minutes into my foray into asyncio (turns out that jupyter notebooks use asyncio internally). There are ways around that (spawn a separate thread with a dedicated event loop, then block), or monkey patch asyncio, but they are all ugly.

camgunz 1y ago

Python, for example, will let you call async functions inside non-async functions, you just have to set up the event loop yourself. This isn't conceptually different than the Io thing here.

throwawaymaths 1y ago
except you cant "pass the same event loop in multiple locations". its also not an easy lift. the zig std will provide a few standard implementations which would be trivial to drop in.
- camgunz 1y ago
  I thought it was the exact same; an event loop in Python is just whatever Io is in Zig, make it a param, get it from an import and a lookup (`import asyncio; loop = asyncio.get_running_loop()`). I might be misunderstanding what you're saying though.
  - deleted 1y ago
    [deleted]
  - throwawaymaths 1y ago
    hm maybe. i guess ive only used python in situations where it injects it into amain so i could have been confused. i thought python async was a wrapper around generators, and so the mechanism cant be instantiated in multiple places. i stand corrected.
    - camgunz 1y ago
      Oh no you're right it's a pain in the ass and weird. But I think it's the way because there's no good reason to have more than one event loop. Also... maybe it started out as generator wrappers? I think I read something that said that.
      - Spivak 1y ago
        > no good reason to have more than one event loop Per thread—once you start working in multiple threads you have the choice to have one global event loop, which comes at the cost of all async code being effectively serialized as far as threads are concerned*, or one event loop per thread. * Which can be fine if your program is mostly not async but you have that one stubborn library. Yay async virality.
        camgunz 1y ago
        I can't say there's no good reason to have per thread event loops, but I think I can say if you do know of one you're suffering a terrible curse. I can only imagine the constraints that would force me to do this.
        Spivak 1y ago
        Because you have a main application running a web server and a daemon worker thread performing potentially long running tasks that use async libraries and you don't want to block the responsiveness of your web server. It's really not that bad, at least in Python.
        camgunz 1y ago
        Well, here we go I guess. Why can't you just use FastAPI? Or Tornado? Isn't there also an async Flask? Isn't Django also async now? What minor god have you angered to be chained to a non-async framework?
        1y ago
gpderetta 1y ago
But the asyncio event loop is not reentrant, so your faux sync functions cannot be safely called from other async functions. It is an extremely leaky abstraction. This is not a theoretical possibility, I stumbled on the issue 15 minutes into my foray into asyncio (turns out that jupyter notebooks use asyncio internally). There are ways around that (spawn a separate thread with a dedicated event loop, then block), or monkey patch asyncio, but they are all ugly.