向字符串中的所有非单词字符添加反斜杠

Question

由于我想把一个list(url_key)中string的每个元素做成regex来识别另一个list中的元素是否有模式，所以我需要给所有非word加反斜杠url_key 中每个元素的字符使用 python。

我的代码示例：

import re
sentences = ["Disallow DCCP sockets due to such NFC-3456",
            "Check at http://www.n.io/search?query=title++sub/file.html",
            "Specifies the hash algorithm on them"]

url_key = ['www.n.io/search?query=title++sub', 'someweb.org/dirs.io']    # there are thousands of elements
add_key = ['NFC-[0-9]{4}', 'CEZ-[0-9a-z]{4,8}']    # there are hundreds of elements

pattern = url_key + add_key
mykey = re.compile('(?:% s)' % '|'.join(pattern))

for item in sentences:
    if mykey.search(item):
        print (item, ' --> Keyword is found')
    else:
        print (item, ' --> Keyword is not Found')

但是这段代码给我一个错误：

error                             Traceback (most recent call last)
<ipython-input-80-5348ee9c65ec> in <module>()
      8 
      9 pattern = url_key + add_key
---> 10 mykey = re.compile('(?:% s)' % '|'.join(pattern))
     11 
     12 for item in sentences:

~/anaconda3/lib/python3.6/re.py in compile(pattern, flags)
    231 def compile(pattern, flags=0):
    232     "Compile a regular expression pattern, returning a pattern object."
--> 233     return _compile(pattern, flags)
    234 
    235 def purge():

~/anaconda3/lib/python3.6/re.py in _compile(pattern, flags)
    299     if not sre_compile.isstring(pattern):
    300         raise TypeError("first argument must be string or compiled pattern")
--> 301     p = sre_compile.compile(pattern, flags)
    302     if not (flags & DEBUG):
    303         if len(_cache) >= _MAXCACHE:

~/anaconda3/lib/python3.6/sre_compile.py in compile(p, flags)
    560     if isstring(p):
    561         pattern = p
--> 562         p = sre_parse.parse(p, flags)
    563     else:
    564         pattern = None

~/anaconda3/lib/python3.6/sre_parse.py in parse(str, flags, pattern)
    853 
    854     try:
--> 855         p = _parse_sub(source, pattern, flags & SRE_FLAG_VERBOSE, 0)
    856     except Verbose:
    857         # the VERBOSE flag was switched on inside the pattern.  to be

~/anaconda3/lib/python3.6/sre_parse.py in _parse_sub(source, state, verbose, nested)
    414     while True:
    415         itemsappend(_parse(source, state, verbose, nested + 1,
--> 416                            not nested and not items))
    417         if not sourcematch("|"):
    418             break

~/anaconda3/lib/python3.6/sre_parse.py in _parse(source, state, verbose, nested, first)
    763                 sub_verbose = ((verbose or (add_flags & SRE_FLAG_VERBOSE)) and
    764                                not (del_flags & SRE_FLAG_VERBOSE))
--> 765                 p = _parse_sub(source, state, sub_verbose, nested + 1)
    766             if not source.match(")"):
    767                 raise source.error("missing ), unterminated subpattern",

~/anaconda3/lib/python3.6/sre_parse.py in _parse_sub(source, state, verbose, nested)
    414     while True:
    415         itemsappend(_parse(source, state, verbose, nested + 1,
--> 416                            not nested and not items))
    417         if not sourcematch("|"):
    418             break

~/anaconda3/lib/python3.6/sre_parse.py in _parse(source, state, verbose, nested, first)
    617             if item[0][0] in _REPEATCODES:
    618                 raise source.error("multiple repeat",
--> 619                                    source.tell() - here + len(this))
    620             if sourcematch("?"):
    621                 subpattern[-1] = (MIN_REPEAT, (min, max, item))

error: multiple repeat at position 31

预期结果：

Disallow DCCP sockets due to such NFC-3456 --> Keyword is found 
Check at http://www.n.io/search?query=title++sub/file.html --> Keyword is found
Specifies the hash algorithm on them --> Keyword is not found

如有任何帮助，我们将不胜感激。谢谢。

Answer 1

您应该使用原始字符串：

result = re.sub('(\W)', r'\', mystring)

或者转义反斜杠：

result = re.sub('(\W)', '\\\1', mystring)

Answer 2

您的主要问题是字符串转义在正则表达式替换转义之前生效。切换到原始字符串（以禁止字符串转义）并转义反斜杠（因为 \ 本身就是一个替换转义）将解决这个问题：

>>> print(re.sub(r'(\W)', r'\', '?:n.io/search?query=title++sub'))
\?\:n\.io\/search\?query\=title\+\+sub

请注意，您可能不需要如此广泛的转义。如果你只是想转义正则表达式的特殊字符，re.escape 会为你做这个：

>>> print(re.escape('?:n.io/search?query=title++sub'))
\?:n\.io/search\?query=title\+\+sub

不添加不必要的转义（那些不需要对正则表达式字符进行反专业化的转义）。

向字符串中的所有非单词字符添加反斜杠

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