【Python】非同期処理を理解する

### 非同期処理とは？
あるタスクが終了するのを待っている間、別のタスクを実行すること

$ pip3 install aiohttp

import datetime
import aiohttp
import asyncio

start = datetime.datetime.now()

def log(message):
    print(f'{(datetime.datetime.now() - start).seconds}秒経過', message)

async def fetch(session, url):
    """ 非同期にURLからデータを取得 """
    print(f"Fetching {url}")
    async with session.get(url) as response:
        return await response.text()

async def main():
    log("タスク開始")
    urls = [
        "http://google.com",
        "http://qiita.com",
        "https://www.python.org/",
        "https://www.mozilla.org/en-US/",
        "https://html.spec.whatwg.org/multipage/",
        "https://www.w3.org/TR/css/",
        "https://ecma-international.org/",
        "https://www.typescriptlang.org/",
        "https://www.oracle.com/jp/java/technologies/",
        "https://www.ruby-lang.org/ja/",
        "https://www.postgresql.org/",
        "https://www.mysql.com/jp/",
        "https://docs.djangoproject.com/ja/5.0/",
        "https://spring.pleiades.io/projects/spring-boot",
        "https://rubyonrails.org/"
        "https://firebase.google.com/?hl=ja",
        "https://go.dev/",
        "https://nodejs.org/en"
    ]

    async with aiohttp.ClientSession() as session:
        tasks = [fetch(session, url) for url in urls]

        print("Starting tasks...")

        print("Tasks are running in the background...")

        results = await asyncio.gather(*tasks)

        for result in results:
            print(result[:100])

    log("task finished")

if __name__ == "__main__":
    asyncio.run(main())