How do I actually use promises?

[ttulttul]

Can you guys please provide a practical example of using promises to use the API asynchronously? It's just super unclear, and nothing I'm trying is working.

[pkopac]

Hi @ttulttul,

we have examples in the README - Usage. Further details can be found in the library documentation.
But basically, you just need to chain .then(handler) to receive responses and .catch(handler) to receive errors. Let us know, if you keep running into some specific error.

[ttulttul]

Thanks. I got this basically working. Now, I'm confused as to why the promises system seems to be running only one asynchronous request at a time. I was expecting things to go a lot faster, in other words.. Is there a way to control the level of parallelism?

[ttulttul]

I can sort of answer my own question here. No, is the simple answer. This library uses Promises, but does not tie into an asynchronous requests library such as grequests. Therefore, the HTTP requests are all blocking. That really sucks.

[pkopac]

@ttulttul: I see what you mean. I've tested the library locally and you are right.
That is indeed unexpected 🤔
It seems that you could enable asynchronous scheduling with:

from promise import Promise, set_default_scheduler
from promise.schedulers.asyncio import AsyncioScheduler
...
set_default_scheduler(AsyncioScheduler())

From syrusakbary/promise#45

But I've tried their code example locally and it still worked synchronously for me. I'll have to look into this more deeply, but maybe you can try it in the meanwhile? Perhaps I'm doing something wrong.

[pkopac]

Update: I found an ugly workaround, see syrusakbary/promise#45 (comment) I think the promise library has 2 bugs that cause it to fall back to synchronicity.

[chtseac]

Hello @pkopac, I don't have time to test it with my code, but have you tried using the syntax Promise.promisify(func)() instead of Promise.resolve("foo").then(func, None)? I think that this is a slightly less ugly workaround.

[pkopac]

@chtseac: thanks for the hint with additional (). I tried the method, of course, but this didn't occur to me! Anyway, it doesn't work either. syrusakbary/promise#45 (comment)