迭代列表并删除重复元素时循环问题 [英] Loop problem while iterating through a list and removing recurring elements

问题描述

我想遍历列表，并删除多次计数的项目，因此for循环不会重复打印它们。

I want to iterate through a list, and remove the items that count more than once, so they don't get printed repeatedly by the for loop.

但是，列表中只出现一次的某些项目似乎也受此影响，我无法弄清楚原因。

However, some items appearing only one time in the list seem to get affected too by this, and I can't figure out why.

任何输入都将不胜感激。

Any input would be greatly appreciated.

示例输出：

listy = [2,2,1,3,4,2,1,2,3,4,5]
for i in listy:
  if listy.count(i)>1:
    print i, listy.count(i)
    while i in listy: listy.remove(i)
  else:
    print i, listy.count(i)

输出：

 2 4
 3 2
 1 2

因此完全忽略了4和5.

thus ignoring completely 4 and 5.

推荐答案

迭代时不应修改列表。这应该有效：

You should not modify a list while iterating over it. This one should work:

listy = [2,2,1,3,4,2,1,2,3,4,5]
found = set()
for i in listy:
    if not i in found:
        print i, listy.count(i)
        found.add(i)

结果是：

2 4
1 2
3 2
4 2
5 1

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