在python中使用enumerate()时从列表中删除元素 [英] Remove element from list when using enumerate() in python

问题描述

Object是一个解码的json对象，其中包含一个称为items的列表.

Object is a decoded json object that contains a list called items.

obj = json.loads(response.body_as_unicode())

for index, item in enumerate(obj['items']):
   if not item['name']:
       obj['items'].pop(index)

我遍历这些项目，并希望在满足特定条件时删除该项目.但是，这没有按预期方式工作.经过一番研究，我发现无法同时从python中删除此列表中的项目.但是我不能将提到的解决方案应用于我的问题.我尝试了一些其他方法，例如

I iterate over those items and want to remove an item when a certain condition is met. However this is not working as expected. After some research I found out that one cannot remove items from a list while at the same time iterating of this list in python. But I cannot apply the mentioned solutions to my problem. I tried some different approaches like

obj = json.loads(response.body_as_unicode())
items = obj['items'][:]

for index, item in enumerate(obj['items']):
   if not item['name']:
       obj['items'].remove(item)

但是，这将删除所有项，而不仅仅是没有名称的项.有什么想法可以解决这个问题吗?

But this removes all items instead of just the one not having a name. Any ideas how to solve this?

推荐答案

在迭代列表时不要从列表中删除项目；迭代将跳过项目，因为迭代索引未更新以说明已删除元素

Don't remove items from a list while iterating over it; iteration will skip items as the iteration index is not updated to account for elements removed.

相反，使用

Instead, rebuild the list minus the items you want removed, with a list comprehension with a filter:

obj['items'] = [item for item in obj['items'] if item['name']]

或首先创建列表的副本进行迭代，以使删除不会更改迭代:

or create a copy of the list first to iterate over, so that removing won't alter iteration:

for item in obj['items'][:]:  # [:] creates a copy
   if not item['name']:
       obj['items'].remove(item)

您确实创建了一个副本，但是然后通过循环从静止状态删除的列表来忽略该副本.

You did create a copy, but then ignored that copy by looping over the list that you are deleting from still.

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