Challenge 2: Timed Sequential vs Concurrent Coroutines — Possible Solution
====================================================================

import asyncio
import time

async def download(name):
    print(f"{name}: starting")
    await asyncio.sleep(2)
    print(f"{name}: done")

async def main():
    # sequential
    start = time.time()
    for i in range(3):
        await download(f"file{i}")
    sequential_time = time.time() - start
    print(f"Sequential: {sequential_time:.2f}s")

    # concurrent
    start = time.time()
    await asyncio.gather(
        download("fileA"),
        download("fileB"),
        download("fileC"),
    )
    concurrent_time = time.time() - start
    print(f"Concurrent: {concurrent_time:.2f}s")

asyncio.run(main())

Output (timing will vary slightly, but always roughly this shape):
Sequential: 6.01s
Concurrent: 2.01s

WHY THIS WORKS AS AN ANSWER
------------------------------
The sequential block reuses this chapter's own download(name)
coroutine, called three times with await inside an ordinary for loop
(Course 1, Chapter 4) — each await download(...) fully completes,
including its 2-second asyncio.sleep(2), before the loop moves to the
next iteration, so three calls take roughly 3 x 2 = 6 seconds total,
just like Chapter 3's sequential threading challenge but using
coroutines instead of plain function calls.

The concurrent block reuses this chapter's own asyncio.gather()
example exactly, passing three separate download(...) coroutine calls
to it at once. Because each one hits await asyncio.sleep(2) and hands
control back to the event loop rather than blocking, all three
"waits" overlap on the SAME single thread — bringing total time down
to roughly 2 seconds, directly paralleling Chapter 3's own
threading-vs-sequential timing result, but achieved here with zero
extra threads at all.

time.time() before and after each block reuses the same before/after
timing pattern from Chapter 3's own threading challenge, applied here
to make the sequential-vs-concurrent speed difference directly visible
rather than just asserted.