Improved the asyncio-prompt example.

Author: jonathanslenders

examples/prompts/asyncio-prompt.py

@@ -1,6 +1,6 @@
 #!/usr/bin/env python
 """
-(Python >= 3.5)
+(Python >= 3.6)
 This is an example of how to prompt inside an application that uses the asyncio
 eventloop. The ``prompt_toolkit`` library will make sure that when other
 coroutines are writing to stdout, they write above the prompt, not destroying
@@ -19,18 +19,20 @@
 from prompt_toolkit.patch_stdout import patch_stdout
 from prompt_toolkit.shortcuts import PromptSession
 
-loop = asyncio.get_event_loop()
 
 
 async def print_counter():
  """
  Coroutine that prints counters.
  """
- i = 0
- while True:
- print('Counter: %i' % i)
- i += 1
- await asyncio.sleep(3)
+ try:
+ i = 0
+ while True:
+ print('Counter: %i' % i)
+ i += 1
+ await asyncio.sleep(3)
+ except asyncio.CancelledError:
+ print('Background task cancelled.')
 
 
 async def interactive_shell():
@@ -49,16 +51,20 @@ async def interactive_shell():
  return
 
 
-def main():
+async def main():
  with patch_stdout():
- shell_task = asyncio.ensure_future(interactive_shell())
- background_task = asyncio.gather(print_counter(), return_exceptions=True)
-
- loop.run_until_complete(shell_task)
- background_task.cancel()
- loop.run_until_complete(background_task)
+ background_task = asyncio.create_task(print_counter())
+ try:
+ await interactive_shell()
+ finally:
+ background_task.cancel()
  print('Quitting event loop. Bye.')
 
 
 if __name__ == '__main__':
- main()
+ try:
+ from asyncio import run
+ except ImportError:
+ asyncio.run_until_complete(main())
+ else:
+ asyncio.run(main())