python列表反转

使用reverse来让列表反转特别方便, 没事自己写了几种方式

In [59]: def reverse(nums):
             length = len(nums)
             for i in range(length-1):
                 nums.insert(length-i-1, nums.pop(0))
                 print nums
   ....:         

In [60]: 

In [60]: 

In [60]: a = range(5)

In [61]: reverse(a)
[1, 2, 3, 4, 0]
[2, 3, 4, 1, 0]
[3, 4, 2, 1, 0]
[4, 3, 2, 1, 0]

In [62]: a
Out[62]: [4, 3, 2, 1, 0]

In [63]: 

根据结果能看出, insert操作的执行顺序是先删除, 后插入

In [67]: def reverse(nums):
             i, j = 0, len(nums)-1
             while i < j:
                 nums[i], nums[j] = nums[j], nums[i]
                 i, j = i+1, j-1
                 print nums


In [69]: a = range(5)

In [70]: a
Out[70]: [0, 1, 2, 3, 4]

In [71]:

In [71]: reverse(a)
[4, 1, 2, 3, 0]
[4, 3, 2, 1, 0]

In [72]: a
Out[72]: [4, 3, 2, 1, 0]

In [73]: 

以上两种都是原地操作

In [78]: a
Out[78]: [0, 1, 2, 3, 4]

In [79]: 

In [79]: b = []

In [80]: def reverse(nums):
   ....:     for i in nums:
   ....:         b.insert(0, i)
   ....:         

In [81]: 

In [81]: reverse(a)

In [82]: 

In [82]: b
Out[82]: [4, 3, 2, 1, 0]

In [83]: id(a)
Out[83]: 140434157093160

In [84]: id(b)
Out[84]: 140434157062984

In [85]: