March 2018
Beginner to intermediate
624 pages
16h 10m
Japanese
Content preview from Head First Python 第2版 ―頭とからだで覚えるPythonの基本
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さらなる問題
入出力は（ときどき）遅い
現在、この
Web
アプリケーションはデータベースとほぼ瞬時に通信しているので、ユーザは
Web
アプリケーションがデータベースとやり取りする際の遅延の時間にほとんど気付くことはな
いでしょう。しかし、データベースとのやり取りに時間（おそらく数秒）がかかるとしたらどうな
るでしょうか。
3
長い時間がかかったら？
データベースが別のマシン、別の建物、別の大陸にあるとします。すると何が起こるで
しょうか？
バックエンドデータベースとの通信には時間がかかることがあります。実際には、コードが外
部とやり取りするときにはいつでもそれなりの時間がかかり、通常その時間は制御できません。
制御できないにもかかわらず、長い時間がかかる操作もあります。
この問題を検証したいので、（標準ライブラリの
time
モジュールに含まれる
sleep
関数で）
Web
アプリケーションに人工的な遅延を加えましょう。
Web
アプリケーションの先頭（他の
import
文の近く）に次の行を追加します。
from time import sleep
上の
import
文を挿入したら、
log_request
関数の
with
文の前に次の
1
行を挿入します。
sleep(15)
Web
アプリケーションを再起動して検索を開始すると、はっきりわかる遅延がレスポンスに生
じます。遅延としては
15
秒はとても長く感じ、ほとんどのユーザは何かがクラッシュしていると
考えます。
実行！
Web
版の
search4letters
にようこそ！
このフォームを使って検索リクエストを送ってください。 ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.