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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錯誤檢查策略
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197
（涵蓋於後面的「以 % 進行的傳統字串格式化」），那麼在字串之後，傳入
要在該字串中被格式化的所有的值作為其他引數。舉例來說，別呼叫：
logging.debug('foo is %r' % foo)
這不管需要與否都會進行格式化的作業，改為呼叫：
logging.debug('foo is %r', foo)
這只在必要時才會進行格式化（也就是只在呼叫
debug
會產生記錄輸出的
時候，取決於目前的門檻層級）。
遺憾的是，
logging
模組並不支援涵蓋於後面「字串格式化」中更易讀的格
式化做法，只支援「以 % 進行的傳統字串格式化」中涵蓋的過時做法。幸
好，就記錄（logging）用途而言，除了簡單的
%s
與
%r
以外，你很少會需
要任何格式說明符。
預設情況下，門檻層級（threshold level）是
WARNING
，代表
warning
、
error
及
critical
函式都會產生記錄輸出（logging output），而函式
debug
和
info
則不會。想要變更門檻層級，你隨都可以呼叫
logging.getLogger().
setLevel
，傳入模組
logging
所提供的對應常數之一作為唯一引數：
DEBUG
、
INFO
、
WARNING
、
ERROR
或
CRITICAL
。舉例來說，一旦你呼叫：
logging.getLogger().setLevel(logging.DEBUG)
那麼從
debug
到
critical
的所有記錄函式（logging functions）都會產生記
錄輸出，直到你再次變更層級為止。如果後續你呼叫： ...
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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.