TIL: asyncio.gather() Runs Coroutines Concurrently, Not Sequentially

While working with asynchronous code in Python, I stumbled upon a crucial distinction between using await sequentially and utilizing asyncio.gather(). The key difference lies in how coroutines are executed: sequentially or concurrently.

To illustrate this, consider a simple example where we have two asynchronous functions, async_func1 and async_func2, each simulating a 2-second delay. When using await sequentially, the total execution time would be approximately 4 seconds.

import asyncio
import time

async def async_func1():
    await asyncio.sleep(2)
    return "Func1 done"

async def async_func2():
    await asyncio.sleep(2)
    return "Func2 done"

async def main():
    start_time = time.time()
    await async_func1()
    await async_func2()
    print(f"Sequential execution time: {time.time() - start_time} seconds")

asyncio.run(main())

In contrast, using asyncio.gather() allows both functions to run concurrently, resulting in a total execution time of approximately 2 seconds. The asyncio.gather() function enables the execution of multiple coroutines at the same time, significantly improving performance in I/O-bound applications.

Takeaway: Using asyncio.gather() to run coroutines concurrently can drastically reduce overall execution time compared to sequential await statements.

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