Python asyncio with semaphore

sem.py

import asyncio


async def foo(sem, i):
    async with sem:
        print("acquired", i)
        await asyncio.sleep(1)
        print("released", i)


async def main():
    sem = asyncio.Semaphore(2)

    await asyncio.gather(*[foo(sem, i) for i in range(4)])

asyncio.run(main())