在python里创建一个任务(Task)实例

import asyncio
 
async def task_func():
  print('in task_func')
  return 'the result'
 
async def main(loop):
  print('creating task')
  task = loop.create_task(task_func())
  print('waiting for {!r}'.format(task))
  return_value = await task
  print('task completed {!r}'.format(task))
  print('return value: {!r}'.format(return_value))
 
event_loop = asyncio.get_event_loop()
try:
  event_loop.run_until_complete(main(event_loop))
finally:
  event_loop.close()

import asyncio
 
async def task_func():
  print('in task_func, sleeping')
  try:
    await asyncio.sleep(1)
  except asyncio.CancelledError:
    print('task_func was canceled')
    raise
  return 'the result'
 
def task_canceller(t):
  print('in task_canceller')
  t.cancel()
  print('canceled the task')
 
async def main(loop):
  print('creating task')
  task = loop.create_task(task_func())
  loop.call_soon(task_canceller, task)
  try:
    await task
  except asyncio.CancelledError:
    print('main() also sees task as canceled')
 
event_loop = asyncio.get_event_loop()
try:
  event_loop.run_until_complete(main(event_loop))
finally:
  event_loop.close()