函数会使用 asyncio.gather(create_task(task)) 运行两次吗

Question

What will be happened, if I run:

tasks = []
for item in items:
  tasks.append(asyncio.create_task(f(item)))

res = asyncio.gather(*tasks)

Will functions run twice? After create_task and after gather

Answer 1

First, note that you must await asyncio.gather() for them to run at all.

Once that is fixed, the functions will run only once. create_task() submits them to the event loop. After that, they will run during the next await . asyncio.gather() simply ensures that the calling coroutine awaits their completion. For example, this will run them in two portions:

tasks = []
for item in items:
  tasks.append(asyncio.create_task(f(item)))

await asyncio.sleep(1)   # here they are running for a second

res = await asyncio.gather(*tasks)  # here we wait for them to complete