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Asyncio.gather vs asyncio.wait

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问题：Asyncio.gather vs asyncio.wait
回答 0
asyncio.gather()
asyncio.wait()
asyncio.gather()
asyncio.wait()
回答 1
回答 2

问题：Asyncio.gather vs asyncio.wait

asyncio.gather并且asyncio.wait似乎有类似的用法：我有一堆我想执行/等待的异步事情（不一定要等到下一个开始之前完成）。它们使用不同的语法，并且在某些细节上有所不同，但是对我来说，拥有2个功能在功能上有如此大的重叠是非常不切实际的。我想念什么？

点击查看英文原文

asyncio.gather and asyncio.wait seem to have similar uses: I have a bunch of async things that I want to execute/wait for (not necessarily waiting for one to finish before the next one starts). They use a different syntax, and differ in some details, but it seems very un-pythonic to me to have 2 functions that have such a huge overlap in functionality. What am I missing?

回答 0

尽管在一般情况下类似（“为许多任务运行并获取结果”），但是对于其他情况，每个功能都有一些特定的功能：

asyncio.gather()

返回一个Future实例，允许高层任务分组：

import asyncio
from pprint import pprint

import random


async def coro(tag):
    print(">", tag)
    await asyncio.sleep(random.uniform(1, 3))
    print("<", tag)
    return tag


loop = asyncio.get_event_loop()

group1 = asyncio.gather(*[coro("group 1.{}".format(i)) for i in range(1, 6)])
group2 = asyncio.gather(*[coro("group 2.{}".format(i)) for i in range(1, 4)])
group3 = asyncio.gather(*[coro("group 3.{}".format(i)) for i in range(1, 10)])

all_groups = asyncio.gather(group1, group2, group3)

results = loop.run_until_complete(all_groups)

loop.close()

pprint(results)

群组中的所有任务都可以通过调用group2.cancel()甚至取消all_groups.cancel()。另见.gather(..., return_exceptions=True)，

asyncio.wait()

支持在完成第一个任务后或在指定的超时后等待停止，从而降低了操作的精度：

import asyncio
import random


async def coro(tag):
    print(">", tag)
    await asyncio.sleep(random.uniform(0.5, 5))
    print("<", tag)
    return tag


loop = asyncio.get_event_loop()

tasks = [coro(i) for i in range(1, 11)]

print("Get first result:")
finished, unfinished = loop.run_until_complete(
    asyncio.wait(tasks, return_when=asyncio.FIRST_COMPLETED))

for task in finished:
    print(task.result())
print("unfinished:", len(unfinished))

print("Get more results in 2 seconds:")
finished2, unfinished2 = loop.run_until_complete(
    asyncio.wait(unfinished, timeout=2))

for task in finished2:
    print(task.result())
print("unfinished2:", len(unfinished2))

print("Get all other results:")
finished3, unfinished3 = loop.run_until_complete(asyncio.wait(unfinished2))

for task in finished3:
    print(task.result())

loop.close()
点击查看英文原文

Although similar in general cases (“run and get results for many tasks”), each function has some specific functionality for other cases:

asyncio.gather()

Returns a Future instance, allowing high level grouping of tasks:

import asyncio
from pprint import pprint

import random


async def coro(tag):
    print(">", tag)
    await asyncio.sleep(random.uniform(1, 3))
    print("<", tag)
    return tag


loop = asyncio.get_event_loop()

group1 = asyncio.gather(*[coro("group 1.{}".format(i)) for i in range(1, 6)])
group2 = asyncio.gather(*[coro("group 2.{}".format(i)) for i in range(1, 4)])
group3 = asyncio.gather(*[coro("group 3.{}".format(i)) for i in range(1, 10)])

all_groups = asyncio.gather(group1, group2, group3)

results = loop.run_until_complete(all_groups)

loop.close()

pprint(results)

All tasks in a group can be cancelled by calling group2.cancel() or even all_groups.cancel(). See also .gather(..., return_exceptions=True),

asyncio.wait()

Supports waiting to be stopped after the first task is done, or after a specified timeout, allowing lower level precision of operations:

import asyncio
import random


async def coro(tag):
    print(">", tag)
    await asyncio.sleep(random.uniform(0.5, 5))
    print("<", tag)
    return tag


loop = asyncio.get_event_loop()

tasks = [coro(i) for i in range(1, 11)]

print("Get first result:")
finished, unfinished = loop.run_until_complete(
    asyncio.wait(tasks, return_when=asyncio.FIRST_COMPLETED))

for task in finished:
    print(task.result())
print("unfinished:", len(unfinished))

print("Get more results in 2 seconds:")
finished2, unfinished2 = loop.run_until_complete(
    asyncio.wait(unfinished, timeout=2))

for task in finished2:
    print(task.result())
print("unfinished2:", len(unfinished2))

print("Get all other results:")
finished3, unfinished3 = loop.run_until_complete(asyncio.wait(unfinished2))

for task in finished3:
    print(task.result())

loop.close()

回答 1

asyncio.wait 比 asyncio.gather。

顾名思义，asyncio.gather主要集中在收集结果上。它等待一堆期货，并以给定的顺序返回其结果。

asyncio.wait只是等待期货。而不是直接给您结果，而是完成和待处理的任务。您必须手动收集值。

此外，您可以指定等待所有期货完成，或者仅等待第一个期货wait。

点击查看英文原文

asyncio.wait is more low level than asyncio.gather.

As the name suggests, asyncio.gather mainly focuses on gathering the results. it waits on a bunch of futures and return their results in a given order.

asyncio.wait just waits on the futures. and instead of giving you the results directly, it gives done and pending tasks. you have to mannually collect the values.

Moreover, you could specify to wait for all futures to finish or the just the first one with wait.

回答 2

我还注意到，您可以通过简单地指定列表来在wait（）中提供一组协程：

result=loop.run_until_complete(asyncio.wait([
        say('first hello', 2),
        say('second hello', 1),
        say('third hello', 4)
    ]))

而通过仅指定多个协程来完成对collect（）的分组：

result=loop.run_until_complete(asyncio.gather(
        say('first hello', 2),
        say('second hello', 1),
        say('third hello', 4)
    ))
点击查看英文原文

I also noticed that you can provide a group of coroutines in wait() by simply specifying the list:

result=loop.run_until_complete(asyncio.wait([
        say('first hello', 2),
        say('second hello', 1),
        say('third hello', 4)
    ]))

Whereas grouping in gather() is done by just specifying multiple coroutines:

result=loop.run_until_complete(asyncio.gather(
        say('first hello', 2),
        say('second hello', 1),
        say('third hello', 4)
    ))