Python列表删除多个项目 [英] Python List remove multiple items

问题描述

我正在尝试从列表中删除多次出现的值.输出不会删除任何所需的项.

I am trying to remove multiple occurrences of a value from a list.The output does not remove any of the desired items.

def rem(a,li):
try:
    while a in li == True:
        li.remove(a)
    print('Updated list: ',li)
except ValueError:
    print(a,' is not located in the list ',li)

试用功能示例:

L = [1,2,3,45,3,2,3,3,4,5]

rem(2，L)

输出:更新后的列表:[1、2、3、45、3、2、3、3、4、5]

Output: Updated list: [1, 2, 3, 45, 3, 2, 3, 3, 4, 5]

推荐答案

您的代码中有2个错误.第一个是

There are 2 mistakes in your code. The first one is

while a in li == True:实际上，由于li == True为 False ，因此此检查始终返回 False .

while a in li == True: In fact, this check always returns False since li == True is False.

它实际上应该是while (a in li) == True:或while a in li:

此外，如果您尝试仅删除重复个出现的a(即，将第一个出现的a留在其中)，则列表理解将不符合您的需求.您必须在rem()函数内添加一个附加检查，以捕获第一次出现的a，然后然后执行循环:

Also, if you are trying to delete only repeated occurrences of a (i.e. leave the first occurrence of a in) then list comprehension won't suit your needs. You will have to add an additional check inside your rem() function that catches the first occurrence of a and then executes your loop:

def rem(a, li):
  list_length = len(li)
  i = 0
  while (li[i] != a) and (i < list_length):
    i += 1              # skip to the first occurrence of a in li
  i += 1                # increment i 
  while i < list_length:
    if li[i] == a:
      del li[i]
      print('Updated list: ', li)
      list_length -= 1          # decrement list length after removing occurrence of a
    else:
      i += 1

上面的代码段不涉及列表为空或列表中没有cc的情况.我把那些练习留给你.

The code snippet above does not cover the edge cases where the list is empty, or the case a is not in the list. I'll leave those exercises to you.

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