Coroutines and Async/Await

Introduction

Asynchronous programming enables concurrent execution without threading, using coroutines.

Basic Coroutine

async def fetch_data():
    print("Fetching data...")
    await asyncio.sleep(2)  # Simulate I/O
    return {"data": [1, 2, 3]}

# Run coroutine
async def main():
    result = await fetch_data()
    print(result)

asyncio.run(main())

Running Multiple Coroutines

async def task(name, delay):
    print(f"{name} starting")
    await asyncio.sleep(delay)
    print(f"{name} finished")
    return name

async def main():
    # Sequential
    result1 = await task("A", 1)
    
    # Concurrent
    results = await asyncio.gather(
        task("A", 1),
        task("B", 2),
        task("C", 0.5)
    )
    print(results)  # ['A', 'B', 'C']

Tasks and Futures

async def main():
    task = asyncio.create_task(fetch_data())
    # Do other work
    result = await task
    
    # Wait for multiple
    tasks = [asyncio.create_task(task(i)) for i in range(5)]
    await asyncio.gather(*tasks)

Practice Problems

1. Fetch data from multiple URLs concurrently
2. Implement timeout for coroutine
3. Use asyncio.wait() with tasks
4. Create async context manager
5. Handle exceptions in async code