正则表达式的.*?是什么意思 和()

Answer 1

"."是表示匹配所有character:
(Dot.) In the default mode, this matches any character except a newline. If the
DOTALL flag has been specified, this matches any
character including a newline.

"*"是表示匹配0个或者多个
Causes the resulting RE to match 0 or more repetitions of the preceding RE, as
many repetitions as are possible. ab* will match 'a',
'ab', or 'a' followed by any number of 'b's

“*?”关闭贪婪算法
*?, +?, ??The "*", "+", and "?" qualifiers are all greedy; they match
as much text as possible. Sometimes this behaviour isn't desired; if the RE <.*> is matched against
'<H1>title</H1>', it will match the entire string, and
not just '<H1>'. Adding "?" after
the qualifier makes it perform the match in non-greedy or minimal fashion; as few characters as possible will be
matched. Using .*? in the previous expression will match
only '<H1>'.

例子，没有？，会匹配尽量多：
>>> greed_p = re.compile("(a.*?d)")
>>> p = re.compile("(a.*d)")
>>> s="abcdabcd"
>>> print greed_p.findall(s)
['abcd', 'abcd']
>>> print p.findall(s)
['abcdabcd']
>>>

追问

好多英文看不懂 我英文好差

追答

直接看例子好了。你这里的？是用来关闭贪婪算法的。

追问

对了， 高手 可以加下我QQ吗