如何设计正则表达式模式来匹配字符串

Question

import re
text = "**Company** [Click1](call:58200) ******provides*** **housekeeping** **clean***"
bold = re.findall(r'\*{2}(\w+?)\*{2}', text)
print bold

result: ['Company', 'provides', 'housekeeping', 'clean']
expect: ['**Company**', '**housekeeping**']

如何设计regex模式来grep它？你知道吗

Answer 1

你可以试试Lookaround

The lookaround actually matches characters, but then gives up the match, returning only the result: match or no match

(?<!\*)\*{2}\w+?\*{2}(?!\*)

Online demo

示例代码：

import re
p = re.compile(ur'(?<!\*)\*{2}\w+?\*{2}(?!\*)')
test_str = u"**Company** [Click1](call:58200) ******provides*** **housekeeping** **clean***"

re.findall(p, test_str)

图案说明：

  (?<!                     look behind to see if there is not: 
    \*                       '*'
  )                        end of look-behind

   \*{2}                    '*' (2 times)
  \w+?                     word characters (a-z, A-Z, 0-9, _) (1 or more times)
   \*{2}                    '*' (2 times)

   (?!                      look ahead to see if there is not:
     \*                       '*'
   )                        end of look-ahead