#🔒 Running an `async` function in the background at the same time as going forward in `async for` loo

9 messages · Page 1 of 1 (latest)

indigo trout
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Suppose that I have an async for loop of this form:

```async for x in f():
await g(x)```

In this case, the program will wait until g(x) is finished before going on to the next iteration of the for loop. What if I want to do it in parallell? I know that one can use asyncio.gather to run two async tasks in parallell, and is there then some way to run g(x) in parallel with the rest of the loop? Note that I can't simply use asyncio.gather on "all elements of f()", whatever that would mean, because I don't necessarily have all those elements from the start.

fickle hedgeBOT
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@indigo trout

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sudden hornet
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Is the next x reliant on the previous being computed?
What is preventing you from having all x on hand?

storm fox
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I'd use create_task here

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e.g.

tasks = []
async for x in f():
    tasks.append(asyncio.create_task(g(x))) # each g(x) gets to start right away
await asyncio.gather(*tasks) # wait for them all to finish
#

I think nowadays you can use a TaskGroup instead, but I still haven't quite learned how that works

sudden hornet
# indigo trout Suppose that I have an async for loop of this form: ```async for x in f(): ...

Tasks would be great for this
If you are interested in the Task group Reptile mentioned, I would suggest reading up on it
https://superfastpython.com/asyncio-taskgroup/

Super Fast Python
Jason Brownlee
How to use asyncio.TaskGroup - Super Fast Python

A problem with tasks is that it is a good idea to assign and keep track of the asyncio.Task objects. The reason is that if we don’t the tasks may be garbage collected, terminating the task. A helpful solution is to use a TaskGroup to create and manage a collection of tasks. It has a […]

fickle hedgeBOT
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