list extend() 索引，不仅将列表元素插入到末尾

list extend() to index, inserting list elements not only to the end(list extend() 索引，不仅将列表元素插入到末尾)

问题描述

我正在寻找最 Pythonic 的方式来实现列表 extend 函数的一个版本，它扩展到给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']

有没有办法在不建立新列表的情况下做到这一点，像这样?

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，但我有一种预感，它可能会更容易.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

当然可以使用切片索引:

Sure, you can use slice indexing:

a_list[1:1] = b_list

为了演示一般算法，如果您要在假设的自定义 list 类中实现 my_extend 函数，它看起来像这样:

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

但实际上不要让它成为一个函数，只需在需要时使用切片符号即可.

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

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