Synchronization Primitives

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What is the output of the following code?

javascript

import asyncio

running = 0
max_running = 0

async def worker(sem):
    global running, max_running
    async with sem:
        running += 1
        max_running = max(max_running, running)
        await asyncio.sleep(0.05)
        running -= 1

async def main():
    sem = asyncio.Semaphore(2)
    await asyncio.gather(*(worker(sem) for _ in range(5)))
    print(max_running)

asyncio.run(main())

DTypeError: Semaphore() takes no arguments

What is the output of the following code?

javascript

import asyncio

async def waiter(event, results):
    await event.wait()
    results.append("waiter proceeded")

async def setter(event, results):
    results.append("before set")
    event.set()

async def main():
    event = asyncio.Event()
    results = []
    await asyncio.gather(waiter(event, results), setter(event, results))
    print(results)

asyncio.run(main())

A['before set', 'waiter proceeded']

BBoth coroutines hang forever, since the event is never set before waiter checks it.

C['waiter proceeded', 'before set']

DTypeError: Event() takes no arguments

What is the output of the following code?

javascript

import asyncio

async def slow():
    await asyncio.sleep(0.1)
    return "slow"

async def fast():
    await asyncio.sleep(0.01)
    return "fast"

async def main():
    results = []
    for coro in asyncio.as_completed([slow(), fast()]):
        result = await coro
        results.append(result)
    print(results)

asyncio.run(main())

ATypeError: as_completed() takes no arguments

BAlways matches input order, just like gather().

C['slow', 'fast']

D['fast', 'slow']

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