我可以在Python中使用前置元素而不是附加元素来扩展列表吗?

问题描述：

我可以表演

a = [1,2,3]
b = [4,5,6]
a.extend(b)
# a is now [1,2,3,4,5,6]

是否可以执行扩展列表并将新项添加到列表开头的操作?

Is there way to perform an action for extending list and adding new items to the beginning of the list?

喜欢

a = [1,2,3]
b = [4,5,6]
a.someaction(b)
# a is now [4,5,6,1,2,3]

如果重要的话，我使用2.7.5版本.

I use version 2.7.5, if it is important.

答

您可以分配给切片:

a[:0] = b

演示:

>>> a = [1,2,3]
>>> b = [4,5,6]
>>> a[:0] = b
>>> a
[4, 5, 6, 1, 2, 3]

本质上，list.extend()是对list[len(list):]切片的分配.

Essentially, list.extend() is an assignment to the list[len(list):] slice.

您可以在任何位置插入"另一个列表，只需解决该位置的空片即可.

You can 'insert' another list at any position, just address the empty slice at that location:

>>> a = [1,2,3]
>>> b = [4,5,6]
>>> a[1:1] = b
>>> a
[1, 4, 5, 6, 2, 3]