Python list.index在找不到索引时抛出异常 [英] Python list.index throws exception when index not found

问题描述

为什么list.index抛出异常，而不是使用任意值（例如， -1 ）？这背后的想法是什么？

Why does list.index throw an exception, instead of using an arbitrary value (for example, -1)? What's the idea behind this?

对我来说，处理特殊值而不是例外情况看起来更干净。

To me it looks cleaner to deal with special values, rather than exceptions.

编辑：我没有意识到 -1 是一个潜在有效的值。不过，为什么不是别的呢？无价值怎么样？

EDIT: I didn't realize -1 is a potentially valid value. Nevertheless, why not something else? How about a value of None?

推荐答案

因为 -1 本身就是有效的索引。它可以使用不同的值，例如无，但这没有用， -1 可以是在其他情况下（因此 str.find（）），并且仅仅是错误检查，这正是例外情况。

Because -1 is itself a valid index. It could use a different value, such as None, but that wouldn't be useful, which -1 can be in other situations (thus str.find()), and would amount simply to error-checking, which is exactly what exceptions are for.

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