import asyncio
import collections
import time

# Utility function for printing relative timestamps
start = None
def ts():
	global start
	if start is None:
		start = time.time()
	return round(time.time() - start, 3)

async def ayield():
	print(f'{ts()}: Yielding...')
	await asyncio.sleep(0)

async def process_tasks():
	"""
	We have a list of tasks, we process each of them. However, before starting a new task
	and after scheduling a new task we check that no already-running task can continue instead.
	We do this by yielding control (asyncio.sleep(0)) so that any 'returned' await statement
	will be handled first. 
	"""
	q = collections.deque(range(1, 8))
	print(q)
	while len(q):

		await ayield()  # Before creating a task, make sure we treat ready ongoing coros first
		t = q.popleft()

		###########################################################
		# Add an await ayield() here to see a change in behavior
		###########################################################

		print(f'{ts()}: Creating task {t}')
		asyncio.create_task(coro(t))
		await ayield()

async def coro(i):

	print(f'{ts()}: Task {i} started')
	time.sleep(0.8)  # Compute
	print(f'{ts()}: Task {i} computed. Going async')

	await asyncio.sleep(0.5)  # async stuff
	print(f'{ts()}: Task {i} returned from async') 

	time.sleep(0.2)
	print(f'{ts()}: Task {i} finished')
	await ayield()

async def amain():
	print(f'{ts()}: Started (Yield)')
	await process_tasks()
	print(f'{ts()}: Finished (Yield)')
   
if __name__ == '__main__':
    asyncio.run(amain())