Python旋转列表的方式 _Python旋转列表

列表的轮换也已在前面讨论过, 但是这篇特定的文章集中于速记和各种短技巧, 以单行或一个单词实现。此操作对于程序员完成各种任务至关重要。
让我们讨论一下轮换列表的不同方法。
方法1：使用切片
这种特定的方法是通用方法, 通常用于完成此任务, 并且在许多文章中也进行了讨论。给定转数, 只需将后面的切片部分与初始切片的部分连接即可。

# Python3 code to demonstrate # rotation of list # using slice # initializing list test_list = [ 1 , 4 , 6 , 7 , 2 ]# printing original list print ( "Original list : " + str (test_list))# using slicing to left rotate by 3 test_list = test_list[ 3 :] + test_list[: 3 ]# Printing list after left rotate print ( "List after left rotate by 3 : " + str (test_list))# using slicing to right rotate by 3 # back to Original test_list = test_list[ - 3 :] + test_list[: - 3 ]# Printing after right rotate print ( "List after right rotate by 3(back to original) : " + str (test_list))

输出如下：

Original list : [1, 4, 6, 7, 2] List after left rotate by 3 : [7, 2, 1, 4, 6] List after right rotate by 3 ( back to original) : [1, 4, 6, 7, 2]

方法2：使用列表理解
这个问题也可以通过幼稚的方法解决, 但是它的较短实现将借助于列表理解。在这种方法中, 我们只需要在旋转后将索引分配给每个值到特定位置。

# Python3 code to demonstrate # rotation of list # using list comprehension# initializing list test_list = [ 1 , 4 , 6 , 7 , 2 ]# printing original list print ( "Original list : " + str (test_list))# using list comprehension to left rotate by 3 test_list = [test_list[(i + 3 ) % len (test_list)] for i, x in enumerate (test_list)]# Printing list after left rotate print ( "List after left rotate by 3 : " + str (test_list))# using list comprehension to right rotate by 3 # back to Original test_list = [test_list[(i - 3 ) % len (test_list)] for i, x in enumerate (test_list)]# Printing after right rotate print ( "List after right rotate by 3(back to original) : " + str (test_list))

输出如下：

Original list : [1, 4, 6, 7, 2] List after left rotate by 3 : [7, 2, 1, 4, 6] List after right rotate by 3(back to original) : [1, 4, 6, 7, 2]

方法3：使用collections.deque.rotate()
收集模块具有双端队列类, 该类提供rotate(), 这是允许旋转的内置函数。这是鲜为人知的功能, 但实用性更高。

# Python3 code to demonstrate # rotation of list # using rotate() from collections import deque# initializing list test_list = [ 1 , 4 , 6 , 7 , 2 ]# printing original list print ( "Original list : " + str (test_list))# using rotate() to left rotate by 3 test_list = deque(test_list) test_list.rotate( - 3 ) test_list = list (test_list)# Printing list after left rotate print ( "List after left rotate by 3 : " + str (test_list))# using rotate() to right rotate by 3 # back to Original test_list = deque(test_list) test_list.rotate( 3 ) test_list = list (test_list)# Printing after right rotate print ( "List after right rotate by 3(back to original) : " + str (test_list))

输出如下：