列出extend()以建立索引，不仅将列表元素插入到末尾 [英] list extend() to index, inserting list elements not only to the end

问题描述

我正在寻找实现列表extend函数版本的最有效的方法，该方法将扩展到给定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']

是否可以在不建立新列表的情况下做到这一点?

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']

这种方法实际上并没有那么糟糕，但是我预感可能会更容易.可以吗?

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

推荐答案

当然，您可以使用切片索引:

Sure, you can use slice indexing:

a_list[1:1] = b_list

只是为了演示通用算法，如果要在假设的自定义list类中实现my_extend函数，它将看起来像这样:

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

但是实际上并没有使该函数起作用，只是在需要时使用切片符号.

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

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