問題描述

我正在尋找最 Pythonic 的方式來實(shí)現(xiàn)列表 extend 函數(shù)的一個(gè)版本，它擴(kuò)展到給定的索引而不是列表的末尾.

I'm looking for the most pythonic way to implement a version of the list extend function, where it extends to a given index instead of the end of the list.

a_list = [ "I", "rad", "list" ]                                                       
b_list = [ "am", "a" ]
a_list.my_extend( b_list, 1 ) # insert the items from b_list into a_list at index 1

print( a_list ) # would output: ['I', 'am', 'a', 'rad', 'list']

有沒有辦法在不建立新列表的情況下做到這一點(diǎn)，像這樣?

Is there a way to do this without building a new list, like this?

a_list = [ "I", "rad", "list" ]
b_list = [ "am", "a" ]
c_list = []

c_list.extend( a_list[:1] )
c_list.extend( b_list     )
c_list.extend( a_list[1:] )

print( c_list ) # outputs: ['I', 'am', 'a', 'rad', 'list']

這種方法實(shí)際上并沒有那么糟糕，但我有一種預(yù)感，它可能會更容易.可以嗎?

That approach isn't actually so bad, but I have a hunch it could be easier. Could it?

推薦答案

當(dāng)然可以使用切片索引:

Sure, you can use slice indexing:

a_list[1:1] = b_list

為了演示一般算法，如果您要在假設(shè)的自定義 list 類中實(shí)現(xiàn) my_extend 函數(shù)，它看起來像這樣:

Just to demonstrate the general algorithm, if you were to implement the my_extend function in a hypothetical custom list class, it would look like this:

def my_extend(self, other_list, index):
    self[index:index] = other_list

但實(shí)際上不要讓它成為一個(gè)函數(shù)，只需在需要時(shí)使用切片符號即可.

But don't actually make that a function, just use the slice notation when you need to.

這篇關(guān)于list extend() 索引，不僅將列表元素插入到末尾的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網(wǎng)！