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V2EX  ›  Python

python 正则提取一个字符串时如何只返回字符串而不返回边界?

  •  
  •   tommark · Nov 22, 2014 · 6742 views
    This topic created in 4174 days ago, the information mentioned may be changed or developed.
    例如匹配字符串“aaaa<ab>xxx"中尖括号中的ab,用‘\<.*\>'匹配后,返回的结果是<ab>,如何实现返回的结果只有ab呢?
    一种简单的方法是对返回的结果做切片,请问怎么用python正则表达可以做到?
    13 replies    2014-11-24 08:51:55 +08:00
    banbanchs
        1
    banbanchs  
       Nov 22, 2014   ❤️ 1
    加括号,比如\<(.*)\>
    vulgur
        2
    vulgur  
       Nov 22, 2014
    p = re.compile(r'<(.*)>)
    m = p.search(string)
    if m:
    s = m.group(1)
    return s
    tommark
        3
    tommark  
    OP
       Nov 22, 2014
    @banbanchs 试了一下不管用啊
    14
        4
    14  
       Nov 22, 2014
    哈,这个问题好熟悉,以前刚用re,很纠结匹配之后还要去切片甚至多次re多次切片,直到我知道了()之后眼泪掉下来
    tommark
        5
    tommark  
    OP
       Nov 22, 2014
    @banbanchs 不好意思,我自己弄错了,刚才用这个网站http://tool.oschina.net/regex试验结果不对,用python重新做了一下是对了
    decken
        6
    decken  
       Nov 22, 2014 via Android
    @vulgur 如果是用sub替换字符串的时候这样写规则无效哦,还有什么办法吗
    aaaa007cn
        7
    aaaa007cn  
       Nov 22, 2014
    @decken
    RTFM
    https://docs.python.org/3/library/re.html#re.sub
    > Backreferences, such as \6, are replaced with the substring matched by group 6 in the pattern.
    > In string-type repl arguments, in addition to the character escapes and backreferences described above, \g<name> will use the substring matched by the group named name, as defined by the (?P<name>...) syntax. \g<number> uses the corresponding group number; \g<2> is therefore equivalent to \2, but isn’t ambiguous in a replacement such as \g<2>0. \20 would be interpreted as a reference to group 20, not a reference to group 2 followed by the literal character '0'. The backreference \g<0> substitutes in the entire substring matched by the RE.
    xz
        8
    xz  
       Nov 22, 2014
    a="aaaa<ab>xxx"
    re.findall("<(.+)>",a)
    ryd994
        9
    ryd994  
       Nov 23, 2014 via Android
    regex look ahead/behind
    ryd994
        10
    ryd994  
       Nov 23, 2014 via Android
    这题这么简单还用不上capture
    leoleozhu
        11
    leoleozhu  
       Nov 23, 2014 via Android
    前后环视
    cdxem713
        12
    cdxem713  
       Nov 23, 2014 via iPhone
    顺带一问,如果是在js里面要达到同样效果,有没有办法呀
    mhohai
        13
    mhohai  
       Nov 24, 2014
    正则,你知道捕获括号和非捕获括号么?不想匹配,你知道有四种环视么?
    知道一个会有问题么?

    啥都不知道,就别说会正则!

    ————没错,我是愤青!
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