ThreadPoolExecutor の例
https://docs.python.org/ja/3/library/concurrent.futures.html#threadpoolexecutor-example
code:トリッキーな書き方.py
with concurrent.futures.ThreadPoolExecutor(max_workers=5) as executor:
future_to_url = {executor.submit(load_url, url, 60): url for url in URLS}
for future in concurrent.futures.as_completed(future_to_url):
url = future_to_urlfuture
# future.result()
Futureオブジェクトをキーにして辞書を作る
辞書を使って、Futureオブジェクトを作ったときの引数の値が簡単に取得できる