如何从字符串末尾替换一些字符？

Question

我想替换python字符串末尾的字符.我有这个字符串:

 s = "123123"

我想,以取代过去2用x.假设有一个方法叫做replace_last:

 r = replace_last(s, '2', 'x')
 print r
 1231x3

有没有内置或简单的方法来做到这一点？

Answer 1

这正是rpartition函数用于:

rpartition(...)S.rpartition(sep) - >(head,sep,tail)

Search for the separator sep in S, starting at the end of S, and return
the part before it, the separator itself, and the part after it.  If the
separator is not found, return two empty strings and S.

我写了这个函数,展示了如何rpartition在你的用例中使用:

def replace_last(source_string, replace_what, replace_with):
    head, _sep, tail = source_string.rpartition(replace_what)
    return head + replace_with + tail

s = "123123"
r = replace_last(s, '2', 'x')
print r

输出:

1231x3

Answer 2

使用正则表达式函数re.sub替换字符串末尾的单词

import re
s = "123123"
s = re.sub('23$', 'penguins', s)
print s

打印:

1231penguins

要么

import re
s = "123123"
s = re.sub('^12', 'penguins', s)
print s

打印:

penguins3123

Answer 3

这是少数几个没有左右版本的字符串函数之一,但我们可以使用一些字符串函数来模仿行为.

>>> s = '123123'
>>> t = s.rsplit('2', 1)
>>> u = 'x'.join(t)
>>> u
'1231x3'

要么

>>> 'x'.join('123123'.rsplit('2', 1))
'1231x3'

Answer 4

>>> s = "aaa bbb aaa bbb"
>>> s[::-1].replace('bbb','xxx',1)[::-1]
'aaa bbb aaa xxx'

第二个例子

>>> s = "123123"
>>> s[::-1].replace('2','x',1)[::-1]
'1231x3'

Answer 5

当想要的匹配位于字符串末尾时，re.sub就会出现。

>>> import re
>>> s = "aaa bbb aaa bbb"
>>> s
'aaa bbb aaa bbb'
>>> re.sub('bbb$', 'xxx', s)
'aaa bbb aaa xxx'
>>>