January 2018
Intermediate to advanced
856 pages
17h 17m
Chinese
Content preview from Python 技術手冊 第三版
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第 10 章 檔案與文字作業
記憶體內部的「檔案」：io.StringIO 和
io.BytesIO
你可以撰寫提供你所需方法的 Python 類別來實作類檔案物件（file-like
objects）。如果你想要的只是資料留存在記憶體中，而非在作業系統所見
的檔案上，就用
io
模組的類別
StringIO
或
BytesIO
。它們之間的差異在
於，
StringIO
的實體是文字模式的「檔案」，所以讀取或寫入會消耗或產生
Unicode 字串，而
BytesIO
的實體是二進位的「檔案」，所以讀取或寫入會
消耗或產生 bytestrings（位元組字串）。
實體化其中任一個類別時，你可以選擇性地傳入一個字串引數，分別是
Unicode 或 bytes，來用作該「檔案」的初始內容。兩者中任一個類別的實
體
f
，除了「檔案」的方法，還提供一個額外的方法：
getvalue f.getvalue()
將
f
目前的資料內容回傳為一個字串（文字的或位元組的）。你無法在呼
叫
f.close
之後呼叫
f.getvalue
：
close
會釋放
f
內部所維護的緩衝區，而
getvalue
需要回傳該緩衝區作為結果。
壓縮檔
儲存空間和傳輸頻寬越來越便宜與充沛，但在許多情況中，你可以藉由壓
縮（compression），花費一些額外的計算成本來節省這種資源。計算能力
變便宜且充裕的速度甚至比其他的某些資源（例如頻寬）還要快，所以壓
縮受歡迎的程度持續增長。Python 能讓你的程式輕易地支援壓縮，因為
Python 標準程式庫含有數個壓縮專用的模組。 ...
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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.