#!/usr/bin/env python3

# spinner_await.py

# credits: Example by Luciano Ramalho inspired by

# Michele Simionato's multiprocessing example in the python-list:

# https://mail.python.org/pipermail/python-list/2009-February/538048.html

import asyncio

import itertools

import sys

async def spin(msg): # <1>

write, flush = sys.stdout.write, sys.stdout.flush

for char in itertools.cycle('|/-\\'):

status = char + ' ' + msg

write(status)

flush()

write('\x08' * len(status))

try:

await asyncio.sleep(.1) # <2>

except asyncio.CancelledError: # <3>

break

write(' ' * len(status) + '\x08' * len(status))

async def slow_function(): # <4>

# pretend waiting a long time for I/O

await asyncio.sleep(3) # <5>

return 42

async def supervisor(): # <6>

spinner = asyncio.ensure_future(spin('thinking!')) # <7>

print('spinner object:', spinner) # <8>

result = await slow_function() # <9>

spinner.cancel() # <10>

return result

def main():

loop = asyncio.get_event_loop() # <11>

result = loop.run_until_complete(supervisor()) # <12>

loop.close()

print('Answer:', result)

if __name__ == '__main__':

main()