我可以使用prepend元素扩展Python中的列表而不是追加吗？

Question

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]

有没有办法执行扩展列表和将新项添加到列表开头的操作？

像这样

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

我使用版本2.7.5,如果它很重要.

Answer 1

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):]切片的赋值.

您可以在任何位置"插入"另一个列表,只需在该位置找到空切片:

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

Answer 2

这是你需要的;-)

a = b + a