Python 3.7 ContextVar example in asyncio

test.py

from contextvars import ContextVar

import asyncio
import random

cv = ContextVar('cv')


async def waiting_func(name):
    print(f'{name} Before sleep: {cv.get() == name}')
    await asyncio.sleep(random.random())
    print(f'{name} After 1 sleep: {cv.get() == name}')
    await asyncio.sleep(random.random())
    print(f'{name} After 2 sleep: {cv.get() == name}')


async def task(name):
    asyncio.ensure_future(waiting_func(name))


async def main():
    for name in ('first', 'second', 'third'):
        cvt = cv.set(name)
        await task(name)
        cv.reset(cvt)

asyncio.ensure_future(main())
asyncio.get_event_loop().run_until_complete(asyncio.sleep(4))