【python cookbook】 将字符串逐字符或逐词反转

反转字符最简单的方法是使用步长为-1的方法

revchars = astring[::-1]

反转字符串 应先创建一个单词列表 再将列表反转 在用join方法合并

rewords = astring.split()
rewords.reverse()
rewords = ' '.join(rewords)

#也可以用一行代码表示
rewords = ' '.join(astring.split()[::-1])

逐词反转还保留原来空格的话

import re
revwords = re.split(r'(\s+)',astring)
revwords.reverse()
revwords = ' '.join(revwords)

#一行表示
revwords = ''join(re.split(r'(\s+)',astring)[::-1])

也可使用reversed来替换切片指示符[::-1]

revwords = ''join(reversed(astring.split()))

reverse()

list.reverse()

Reverse the elements of the list, in place.

>>> a
[66.25, -1, 333, 1, 1234.5, 333]
>>> a.reverse()
>>> a
[333, 1234.5, 1, 333, -1, 66.25]

reversed()

reversed(seq)

Return a reverse iterator. seq must be an object which has a __reversed__() method or supports the sequence protocol (the __len__() method and the __getitem__() method with integer arguments starting at 0).

Changed in version 2.6: Added the possibility to write a custom __reversed__() method.

join用法

>>> a="abcd"
>>> ",".join(a)
'a,b,c,d'
>>> "|".join(['a','b','c'])
'a|b|c'
>>> ",".join(('a','b','c'))
'a,b,c'
>>> ",".join({'a':1,'b':2,'c':3})
'a,c,b'