在Python中搜索列表的最快方法 [英] Fastest way to search a list in python

问题描述

当你在中做一些像test这样的事情，其中​​ a 是一个列表，python会执行顺序搜索在列表上还是创建一个哈希表表示来优化查找？在应用程序中，我需要这样做，因为我将在列表上做很多查找，所以最好做一些类似于 b = set（a）然后testin b ？另外请注意，我将拥有的值列表将不会有重复的数据，我实际上并不关心它所处的顺序;我只需要能够检查一个值的存在。


解决方案

还要注意我将拥有的价值清单将不会有重复的数据，我实际上并不关心它的订单;我只需要能够检查一个值的存在。

不要使用列表，使用 set（） 测试中快速的。

我已经看到了20倍的加速和更高的地方（主要是大数字嘎吱嘎吱），其中一个列表更改为一套。

When you do something like "test" in a where a is a list does python do a sequential search on the list or does it create a hash table representation to optimize the lookup? In the application I need this for I'll be doing a lot of lookups on the list so would it be best to do something like b = set(a) and then "test" in b? Also note that the list of values I'll have won't have duplicate data and I don't actually care about the order it's in; I just need to be able to check for the existence of a value.

解决方案

Also note that the list of values I'll have won't have duplicate data and I don't actually care about the order it's in; I just need to be able to check for the existence of a value.

Don't use a list, use a set() instead. It has exactly the properties you want, including a blazing fast in test.

I've seen speedups of 20x and higher in places (mostly heavy number crunching) where one list was changed for a set.

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