python列表取出奇数项,从Python中的列表中删除奇数索引元素

最新推荐文章于 2024-01-08 20:10:46 发布

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最新推荐文章于 2024-01-08 20:10:46 发布

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文章标签： python列表取出奇数项

本文介绍了一种从Python列表中高效移除奇数索引位置元素的方法，避免了直接迭代过程中删除元素导致的问题，并提供了使用切片和列表推导的替代方案。

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I'm trying to remove the odd-indexed elements from my list (where zero is considered even) but removing them this way won't work because it throws off the index values.

lst = ['712490959', '2', '623726061', '2', '552157404', '2', '1285252944', '2', '1130181076', '2', '552157404', '3', '545600725', '0']

def remove_odd_elements(lst):

i=0

for element in lst:

if i % 2 == 0:

pass

else:

lst.remove(element)

i = i + 1

How can I iterate over my list and cleanly remove those odd-indexed elements?

解决方案

You can delete all odd items in one go using a slice:

del lst[1::2]

Demo:

>>> lst = ['712490959', '2', '623726061', '2', '552157404', '2', '1285252944', '2', '1130181076', '2', '552157404', '3', '545600725', '0']

>>> del lst[1::2]

>>> lst

['712490959', '623726061', '552157404', '1285252944', '1130181076', '552157404', '545600725']

You cannot delete elements from a list while you iterate over it, because the list iterator doesn't adjust as you delete items. See Loop "Forgets" to Remove Some Items what happens when you try.

An alternative would be to build a new list object to replace the old, using a list comprehension with enumerate() providing the indices:

lst = [v for i, v in enumerate(lst) if i % 2 == 0]

This keeps the even elements, rather than remove the odd elements.