How to gather task results in Trio?

Returning data: pass the networkID and a dict to the fetch tasks:

async def main():
    …
    results = {}
    async with trio.open_nursery() as nursery:
        for i in networkIds:
            nursery.start_soon(fetch, url.format(i), headers, results, i)
    ## results are available here

async def fetch(url, headers, results, i):
    print("Start: ", url)
    response = await s.get(url, headers=headers)
    print("Finished: ", url, len(response.content), response.status_code)
    results[i] = response

Alternately, create a trio.Queue to which you put the results; your main task can then read the results from the queue.

API limit: create a trio.Queue(10) and start a task along these lines:

async def limiter(queue):
    while True:
        await trio.sleep(0.2)
        await queue.put(None)

Pass that queue to fetch, as another argument, and call await limit_queue.get() before each API call.

Based on this answers, you can define the following function:

async def gather(*tasks):

    async def collect(index, task, results):
        task_func, *task_args = task
        results[index] = await task_func(*task_args)

    results = {}
    async with trio.open_nursery() as nursery:
        for index, task in enumerate(tasks):
            nursery.start_soon(collect, index, task, results)
    return [results[i] for i in range(len(tasks))]

You can then use trio in the exact same way as asyncio by simply patching trio (adding the gather function):

import trio
trio.gather = gather

Here is a practical example:

async def child(x):
    print(f"Child sleeping {x}")
    await trio.sleep(x)
    return 2*x

async def parent():
    tasks = [(child, t) for t in range(3)]
    return await trio.gather(*tasks)

print("results:", trio.run(parent))