如何在Python中的for循环中删除列表元素? [英] How to remove list elements in a for loop in Python?

问题描述

我有一个清单

a = ["a", "b", "c", "d", "e"]

我想在如下所示的for循环中删除此列表中的元素:

I want to remove elements in this list in a for loop like below:

for item in a:
    print item
    a.remove(item)

但是它不起作用.我该怎么办?

But it doesn't work. What can I do?

推荐答案

在使用for循环对其进行迭代时，不允许从列表中删除元素.

You are not permitted to remove elements from the list while iterating over it using a for loop.

重写代码的最佳方法取决于您要执行的操作.

The best way to rewrite the code depends on what it is you're trying to do.

例如，您的代码等效于:

For example, your code is equivalent to:

for item in a:
  print item
a[:] = []

或者，您可以使用while循环:

Alternatively, you could use a while loop:

while a:
  print a.pop(0)

我正在尝试删除符合条件的项目.然后我转到下一个项目.

I'm trying to remove items if they match a condition. Then I go to next item.

您可以将与条件不匹配的每个元素复制到第二个列表中:

You could copy every element that doesn't match the condition into a second list:

result = []
for item in a:
  if condition is False:
    result.append(item)
a = result

或者，您可以使用 filter 或列表解析并分配结果返回到a:

a = filter(lambda item:... , a)

或

a = [item for item in a if ...]

其中...代表您需要检查的条件.

where ... stands for the condition that you need to check.

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