从列表中弹出随机元素的最Python方式是什么? [英] What is the most pythonic way to pop a random element from a list?

问题描述

说我有一个长度未知的列表x，我想从该列表中随机弹出一个元素，以便此后列表中不包含该元素.最Python的方法是什么?

Say I have a list x with unkown length from which I want to randomly pop one element so that the list does not contain the element afterwards. What is the most pythonic way to do this?

我可以使用pop，random.randint和len的组合来方便地做到这一点，并且希望看到更短或更佳的解决方案:

I can do it using a rather unhandy combincation of pop, random.randint, and len, and would like to see shorter or nicer solutions:

import random
x = [1,2,3,4,5,6]
x.pop(random.randint(0,len(x)-1))

我要实现的目标是从列表中连续弹出随机元素. (即，随机弹出一个元素并将其移至字典，随机弹出另一个元素并将其移至另一字典，...)

What I am trying to achieve is consecutively pop random elements from a list. (i.e., randomly pop one element and move it to a dictionary, randomly pop another element and move it to another dictionary, ...)

请注意，我使用的是Python 2.6，没有通过搜索功能找到任何解决方案.

Note that I am using Python 2.6 and did not find any solutions via the search function.

推荐答案

乍一看，您似乎想要做的似乎不太像Python.您不应该从列表的中间删除内容，因为列表在我所知道的所有Python实现中都是作为数组实现的，所以这是一个O(n)操作.

What you seem to be up to doesn't look very Pythonic in the first place. You shouldn't remove stuff from the middle of a list, because lists are implemented as arrays in all Python implementations I know of, so this is an O(n) operation.

如果您确实需要将此功能作为算法的一部分，则应签出类似 blist 支持从中间有效删除.

If you really need this functionality as part of an algorithm, you should check out a data structure like the blist that supports efficient deletion from the middle.

在纯Python中，如果不需要访问其余元素，该怎么办就是先将列表随机播放，然后对其进行遍历:

In pure Python, what you can do if you don't need access to the remaining elements is just shuffle the list first and then iterate over it:

lst = [1,2,3]
random.shuffle(lst)
for x in lst:
  # ...

如果您确实需要剩余部分(有点代码味道，恕我直言)，至少您现在可以从列表末尾pop()(很快！):

If you really need the remainder (which is a bit of a code smell, IMHO), at least you can pop() from the end of the list now (which is fast!):

while lst:
  x = lst.pop()
  # do something with the element      

通常，如果您使用更具功能性的样式，而不是突变状态(就像对列表所做的那样)，通常可以使程序更优雅地表达.

In general, you can often express your programs more elegantly if you use a more functional style, instead of mutating state (like you do with the list).

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