递减要在for循环中递增的变量 [英] Decrement the Variable I'm Incrementing in for loop

问题描述

有点像Python的新手，我环顾了一下，但没有找到令人满意的答案.我在做一些练习题，我想做一个摆脱列表中重复值的方法.到目前为止，这是我的代码:

kind of a newbie to Python and I've looked around a bit but haven't found a satisfying answer to my question. I'm doing some practice problems and I want to make a method that gets rid of duplicate values in a list. So far, this is my code:

def noDouble(nums):
  for x in xrange(len(nums) - 2):
      if nums[x] == nums[x + 1]:
          nums.pop(x)
          x -= 1
  return nums

我想发生的是，如果有重复项，请弹出其中一个重复项，然后再次移回(这样，如果有3个相同编号的实例，它将消除所有通过倒带").

What I want to happen is that if there's a duplicate, pop off one of the duplicates and then move back again (so that if there are, say, 3 instances of the same number, it'll get rid of al of them by 'rewinding').

我正在寻找一个解释，为什么我的代码无法正常工作以及解释性的解决方案，我非常感谢您提供的所有帮助.谢谢.

I'm looking for an explanation for why my code doesn't work as well as an explained solution and I'd really appreciate any and all help. Thanks.

推荐答案

因为for不计算数字；它遍历一个序列.每次循环主体执行时，x都会设置为xrange生成的下一个值. for语句根本不在乎循环结束时x是什么.

Because for doesn't count numbers; it iterates over a sequence. Every time the body of the loop executes, x is set to the next value produced by the xrange. The for statement couldn't care less what x is at the end of the loop.

无论如何，您实际上不应该在循环中修改列表.这样做的更简单方法是建立一个新列表:

You really shouldn't modify a list within a loop over it, anyway. The easier way to do this is to build a new list:

def remove_doubles(old):
    new = []
    for item in old:
        if new and item == new[-1]:
            continue
        new.append(item)
    return new

当然，真正删除重复项的简单方法是list(set(foo)).但这将删除所有重复项，而不仅仅是相邻重复项，并且可能还会破坏项目顺序.

Of course, the really easy way to remove duplicates is list(set(foo)). But that will remove all duplicates, not just adjacent ones, and probably destroy the item order too.

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