python 异步协程

 """A very simple co-routine scheduler.
 Note: this is written to favour simple code over performance.
 """
 from types import coroutine

 @coroutine
 def switch():
     yield

 def run(coros):
     """Execute a list of co-routines until all have completed."""
     # Copy argument list to avoid modification of arguments.
     coros = list(coros)

     while len(coros):
         # Copy the list for iteration, to enable removal from original
         # list.
         for coro in list(coros):
             try:
                 coro.send(None)
             except StopIteration:
                 coros.remove(coro)

 async def coro1():
     print("C1: Start")
     await switch()
     print("C1: a")
     await switch()
     print("C1: b")
     await switch()
     print("C1: c")
     await switch()
     print("C1: Stop")

 async def coro2():
     print("C2: Start")
     await switch()
     print("C2: a")
     await switch()
     print("C2: b")
     await switch()
     print("C2: c")
     await switch()
     print("C2: Stop")

 run([coro1(), coro2()])