Advanced Async Programming

asyncio patterns, tasks, semaphores, and async generators.

Overview

Master advanced async patterns.

Tasks and Gather

import asyncio

async def fetch_data(url, delay):
    print(f"Fetching {url}")
    await asyncio.sleep(delay)
    return f"Data from {url}"

async def main():
    # Run tasks concurrently
    tasks = [
        fetch_data("api1.com", 2),
        fetch_data("api2.com", 1),
        fetch_data("api3.com", 3),
    ]
    
    results = await asyncio.gather(*tasks)
    print(results)

asyncio.run(main())

Semaphores

import asyncio

async def worker(semaphore, name, delay):
    async with semaphore:
        print(f"{name} started")
        await asyncio.sleep(delay)
        print(f"{name} finished")

async def main():
    semaphore = asyncio.Semaphore(3)  # Max 3 concurrent
    
    tasks = [
        worker(semaphore, f"Worker {i}", i)
        for i in range(10)
    ]
    
    await asyncio.gather(*tasks)

asyncio.run(main())

Async Generators

async def async_generator(n):
    for i in range(n):
        await asyncio.sleep(0.1)
        yield i

async def main():
    async for value in async_generator(5):
        print(value)

asyncio.run(main())

Practice

Implement an async web scraper with rate limiting.