正则表达式替换(在Python中)-一种更简单的方法?

>>> import re
>>> s = "start foo end"
>>> s = re.sub("foo", "replaced", s)
>>> s
'start replaced end'
>>> s = re.sub("(?<= )(.+)(?= )", lambda m: "can use a callable for the %s text too" % m.group(1), s)
>>> s
'start can use a callable for the replaced text too end'
>>> help(re.sub)
Help on function sub in module re:

sub(pattern, repl, string, count=0)
    Return the string obtained by replacing the leftmost
    non-overlapping occurrences of the pattern in string by the
    replacement repl.  repl can be either a string or a callable;
    if a callable, it's passed the match object and must return
    a replacement string to be used.

re documentation 看样子 (?=...) 向后看 (?<=...)

使用Python的 re 单元无法改变这一点:

>>> import re
>>> re.sub("(?<=foo)bar(?=baz)", "quux", "foobarbaz")
'fooquuxbaz'
>>> re.sub("(?<=fo+)bar(?=baz)", "quux", "foobarbaz")

Traceback (most recent call last):
  File "<pyshell#2>", line 1, in <module>
    re.sub("(?<=fo+)bar(?=baz)", "quux", string)
  File "C:\Development\Python25\lib\re.py", line 150, in sub
    return _compile(pattern, 0).sub(repl, string, count)
  File "C:\Development\Python25\lib\re.py", line 241, in _compile
    raise error, v # invalid expression
error: look-behind requires fixed-width pattern

这意味着您需要解决这个问题,最简单的解决方案与您现在所做的非常相似:

>>> re.sub("(fo+)bar(?=baz)", "\\1quux", "foobarbaz")
'fooquuxbaz'
>>>
>>> # If you need to turn this into a callable function:
>>> def replace(start, replace, end, replacement, search):
        return re.sub("(" + re.escape(start) + ")" + re.escape(replace) + "(?=" + re.escape + ")", "\\1" + re.escape(replacement), search)

an expert has to say on the matter (他说的是JavaScript,它完全没有lookbehind,但许多原则都是一样的),你会看到他最简单的解决方案看起来很像这个。

我认为最好的方法就是在一个组中捕获您想要替换的任何内容,然后使用捕获的组的开始和结束属性来替换它。

当做

阿德林

#the pattern will contain the expression we want to replace as the first group
pat = "word1\s(.*)\sword2"   
test = "word1 will never be a word2"
repl = "replace"

import re
m = re.search(pat,test)

if m and m.groups() > 0:
    line = test[:m.start(1)] + repl + test[m.end(1):]
    print line
else:
    print "the pattern didn't capture any text"

“word1永远不会是word2”