asyncio

import asyncio
import aiohttp

# async function — returns a coroutine
async def fetch_user(session, user_id: int) -> dict:
    async with session.get(f"/api/users/{user_id}") as response:
        return await response.json()

# Running async functions
async def main():
    async with aiohttp.ClientSession() as session:
        user = await fetch_user(session, 42)
        print(user)

asyncio.run(main())

# Concurrent execution (run multiple at once!)
async def fetch_all_users(user_ids: list[int]) -> list[dict]:
    async with aiohttp.ClientSession() as session:
        tasks = [fetch_user(session, uid) for uid in user_ids]
        return await asyncio.gather(*tasks)  # parallel!

# asyncio.gather vs sequential
# Sequential: 10 requests × 1s each = 10 seconds
# gather:     10 requests × 1s each = ~1 second

import asyncio
import aiohttp
from bs4 import BeautifulSoup

async def fetch_product_price(session: aiohttp.ClientSession, url: str) -> dict:
    try:
        async with session.get(url, timeout=aiohttp.ClientTimeout(total=5)) as resp:
            html = await resp.text()
            soup = BeautifulSoup(html, "html.parser")
            price = soup.select_one(".product-price")
            return {"url": url, "price": price.text if price else "N/A"}
    except Exception as e:
        return {"url": url, "error": str(e)}

async def scrape_all_prices(urls: list[str]) -> list[dict]:
    # Limit concurrent requests to avoid overwhelming servers
    semaphore = asyncio.Semaphore(10)

    async def bounded_fetch(url):
        async with semaphore:
            return await fetch_product_price(session, url)

    async with aiohttp.ClientSession() as session:
        tasks = [bounded_fetch(url) for url in urls]
        return await asyncio.gather(*tasks)

results = asyncio.run(scrape_all_prices(product_urls))