比“尝试"更快的方法和“除外"?- Python [英] Quicker way than "try" and "except" ? - Python

问题描述

我经常写如下代码

try:
  self.title = item.title().content.string
except AttributeError, e:
  self.title = None

<小时>

有没有更快的方法来解决这个问题?单线?

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Is there a quicker way of dealing with this? a one-liner?

推荐答案

item.title() 有哪些例外?光秃秃的 except(可怕的做法！)并没有告诉我们.如果是 AttributeError(例如，item 没有 title 方法)，

What exceptions are you getting from item.title()? The bare except (horrible practice!) doesn't tell us. If it's an AttributeError (where item doesn't have a title method, for example),

self.title = getattr(item, 'title', lambda: None)()

可能是您寻求的单线(但请注意，性能不会很大不同；-).

might be the one-liner you seek (but performance won't be enormously different, mind you;-).

编辑:由于 OP 完全改变了问题(它最初只是使用 self.title()，现在使用 self.title().content.string，并且确实专门捕获 AttributeError 而不是使用裸的 except)，这个答案的先前版本当然不再适用.现在正确的答案是:尝试单行是一种荒谬的方法，当属性引用链越来越长时(下一次会有多少，九个?因为他们从一跳到三)第一次编辑...;-).

Edit: as the OP entirely changed the question (it was originally just using self.title(), it's now using self.title().content.string, and does specifically catch AttributeError rather than using a bare except), the previous version of this answer of course doesn't apply any more. The proper answer now is: attempting a one-liner is an absurd approach, when the chain of attribute references &c keeps growing longer and longer (how many will there be next time, nine? Since they jumped from one to three with the first edit...;-).

并且不知道那么长的许多基本运算中的哪一个，德米特法则-嘲笑引用链可能会引发 AttributeError，任何优化尝试也将是盲目的.

And with no idea of which of the many elementary operations expressed by that long, Law of Demeter-scoffing chain of references might raise the AttributeError, any attempt at optimization would be flying rather blind, too.

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