August 2015
Intermediate to advanced
384 pages
7h 42m
Chinese
Content preview from 高效能PYTHON程式設計
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第二章
圖 2-3 Julia set 的純灰階圖
簡單的計時方法— print 與裝飾器
在範例 2-4 之後，我們看到程式碼的幾個
print
陳述式產生的輸出。在 Ian 的筆電上，
使用 CPython 2.7 時，這段程式碼大約耗費 12 秒鐘。注意，執行時間總是會有一些變
異，在計時你的程式碼時，必須觀察執行時間的正常變異，否則，你可能會誤將程式碼
的改進歸因於執行時間的隨機變動。
在執行你的程式碼時，你的電腦還會執行其他任務，例如，存取網路、磁碟或 RAM，
而這些因素都會對你的程式的執行時間造成變異。
Ian 的筆電是 Dell E6420，具有 Intel Core I7-2720QM CPU（2.20 GHz，6 MB 快取，四
核心）和 8 GB 的 RAM，執行 Ubuntu 13.10。
在
calc_pure_python
（範例 2-2）裡，我們可以看到幾個
print
陳述式，這是
在函式裡
量測一段程式碼的執行時間的最簡單方式。這是非常基本的方法，然而，儘管迅速又隨
性，當你剛看到一段程式碼時，那會是非常有用的。
透過效能分析找出瓶頸
|
27
在偵錯程式碼及進行效能分析時，使用
print
陳述式是很平常的，但很快就會變得不好
管理，然而，對簡單的調查來說還是很有用的。當你使用完畢 ...
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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.