数据分析之正则表达式

数据分析之正则表达式

基础匹配规则

符号	示例	描述
literal	hello	匹配字面字符
re1|re2	he|she	匹配re1或者re2表达式
.	a.b	匹配任意字符（除了\n之外）
[x-y]	[A-Z]	匹配某一个范围内的单一字符
[^…]	[^abc]，[^a-z]	不匹配字符集出现的字符
^	^hello world	匹配以字符串内容为起始的部分
$	hello world$	匹配以字符串内容为结束的部分

控制匹配次数

符号	示例	描述
*	[A-Za-z0-9]*	匹配0次或者多次前面的字母或者数字的组合
+	[a-z]+\.com	匹配1次或者多次前面的字母或者数字的组合
？	[hello]+	匹配0次或者1次前面的字母或者数字的组合
{N}	[0-9]{3}	匹配N个数字
{M,N}	[0-9]{1,3}	匹配M~N次前面的正则表达式

前后格式匹配

符号	示例	描述
(?<=…)	(?<=hel)[a-z]{2}	匹配hel（hello）后面的两个字符
(?=…)	[a-z]{2}(?=rld)	匹配rld（world）前面两个字符
(?	(?	匹配字符串之前不是192.168.开头的字符
(?!..)	(?!.cn)	匹配非.cn的的前面字符

re包源码注释

The special characters are:
    "."      Matches any character except a newline.
    "^"      Matches the start of the string.
    "$"      Matches the end of the string or just before the newline at
             the end of the string.
    "*"      Matches 0 or more (greedy) repetitions of the preceding RE.
             Greedy means that it will match as many repetitions as possible.
    "+"      Matches 1 or more (greedy) repetitions of the preceding RE.
    "?"      Matches 0 or 1 (greedy) of the preceding RE.
    *?,+?,?? Non-greedy versions of the previous three special characters.
    {m,n}    Matches from m to n repetitions of the preceding RE.
    {m,n}?   Non-greedy version of the above.
    "\\"     Either escapes special characters or signals a special sequence.
    []       Indicates a set of characters.
             A "^" as the first character indicates a complementing set.
    "|"      A|B, creates an RE that will match either A or B.
    (...)    Matches the RE inside the parentheses.
             The contents can be retrieved or matched later in the string.
    (?aiLmsux) Set the A, I, L, M, S, U, or X flag for the RE (see below).
    (?:...)  Non-grouping version of regular parentheses.
    (?P<name>...) The substring matched by the group is accessible by name.
    (?P=name)     Matches the text matched earlier by the group named name.
    (?#...)  A comment; ignored.
    (?=...)  Matches if ... matches next, but doesn't consume the string.
    (?!...)  Matches if ... doesn't match next.
    (?<=...) Matches if preceded by ... (must be fixed length).
    (?<!...) Matches if not preceded by ... (must be fixed length).
    (?(id/name)yes|no) Matches yes pattern if the group with id/name matched,
                       the (optional) no pattern otherwise.

re.compile()

re.compile(pattern, flags=0)

编译一个正则表达式

re.match()

re.match(pattern, string, flags=0)

从字符串的起始位置匹配一个模式，匹配失败就返回None.

re.search()

re.search(pattern, string, flags=0)

扫描整个字符串并返回第一个匹配成功的。

re.sub()

re.sub(pattern, repl, string, count=0, flags=0)

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