Python正则表达式指南

妖狐艹你老母 2022-05-21 09:42 161阅读 0赞

https://www.cnblogs.com/huxi/archive/2010/07/04/1771073.html

> 本文介绍了Python对于正则表达式的支持，包括正则表达式基础以及Python正则表达式标准库的完整介绍及使用示例。本文的内容不包括如何编写高效的正则表达式、如何优化正则表达式，这些主题请查看其他教程。
> 
> 注意：本文基于Python2.4完成；如果看到不明白的词汇请记得百度谷歌或维基，whatever。
> 
> 尊重作者的劳动，转载请注明作者及原文地址 >.<html

## 1. 正则表达式基础 ##

### 1.1. 简单介绍 ###

正则表达式并不是Python的一部分。正则表达式是用于处理字符串的强大工具，拥有自己独特的语法以及一个独立的处理引擎，效率上可能不如str自带的方法，但功能十分强大。得益于这一点，在提供了正则表达式的语言里，正则表达式的语法都是一样的，区别只在于不同的编程语言实现支持的语法数量不同；但不用担心，不被支持的语法通常是不常用的部分。如果已经在其他语言里使用过正则表达式，只需要简单看一看就可以上手了。

下图展示了使用正则表达式进行匹配的流程：   
![re\_simple][re_simple]

正则表达式的大致匹配过程是：依次拿出表达式和文本中的字符比较，如果每一个字符都能匹配，则匹配成功；一旦有匹配不成功的字符则匹配失败。如果表达式中有量词或边界，这个过程会稍微有一些不同，但也是很好理解的，看下图中的示例以及自己多使用几次就能明白。

下图列出了Python支持的正则表达式元字符和语法：     
![pyre][]

### 1.2. 数量词的贪婪模式与非贪婪模式 ###

正则表达式通常用于在文本中查找匹配的字符串。Python里数量词默认是贪婪的（在少数语言里也可能是默认非贪婪），总是尝试匹配尽可能多的字符；非贪婪的则相反，总是尝试匹配尽可能少的字符。例如：正则表达式"ab\*"如果用于查找"abbbc"，将找到"abbb"。而如果使用非贪婪的数量词"ab\*?"，将找到"a"。

### 1.3. 反斜杠的困扰 ###

与大多数编程语言相同，正则表达式里使用"\\"作为转义字符，这就可能造成反斜杠困扰。假如你需要匹配文本中的字符"\\"，那么使用编程语言表示的正则表达式里将需要4个反斜杠"\\\\\\\\"：前两个和后两个分别用于在编程语言里转义成反斜杠，转换成两个反斜杠后再在正则表达式里转义成一个反斜杠。Python里的原生字符串很好地解决了这个问题，这个例子中的正则表达式可以使用r"\\\\"表示。同样，匹配一个数字的"\\\\d"可以写成r"\\d"。有了原生字符串，你再也不用担心是不是漏写了反斜杠，写出来的表达式也更直观。

### 1.4. 匹配模式 ###

正则表达式提供了一些可用的匹配模式，比如忽略大小写、多行匹配等，这部分内容将在Pattern类的工厂方法re.compile(pattern\[, flags\])中一起介绍。

## 2. re模块 ##

### 2.1. 开始使用re ###

Python通过re模块提供对正则表达式的支持。使用re的一般步骤是先将正则表达式的字符串形式编译为Pattern实例，然后使用Pattern实例处理文本并获得匹配结果（一个Match实例），最后使用Match实例获得信息，进行其他的操作。

re.compile(strPattern\[, flag\]):

这个方法是Pattern类的工厂方法，用于将字符串形式的正则表达式编译为Pattern对象。 第二个参数flag是匹配模式，取值可以使用按位或运算符'|'表示同时生效，比如re.I | re.M。另外，你也可以在regex字符串中指定模式，比如re.compile('pattern', re.I | re.M)与re.compile('(?im)pattern')是等价的。   
可选值有：

*  re.I(re.IGNORECASE): 忽略大小写（括号内是完整写法，下同）
 *  M(MULTILINE): 多行模式，改变'^'和'$'的行为（参见上图）
 *  S(DOTALL): 点任意匹配模式，改变'.'的行为
 *  L(LOCALE): 使预定字符类 \\w \\W \\b \\B \\s \\S 取决于当前区域设定
 *  U(UNICODE): 使预定字符类 \\w \\W \\b \\B \\s \\S \\d \\D 取决于unicode定义的字符属性
 *  X(VERBOSE): 详细模式。这个模式下正则表达式可以是多行，忽略空白字符，并可以加入注释。以下两个正则表达式是等价的：

re提供了众多模块方法用于完成正则表达式的功能。这些方法可以使用Pattern实例的相应方法替代，唯一的好处是少写一行re.compile()代码，但同时也无法复用编译后的Pattern对象。这些方法将在Pattern类的实例方法部分一起介绍。如上面这个例子可以简写为：

re模块还提供了一个方法escape(string)，用于将string中的正则表达式元字符如\*/+/?等之前加上转义符再返回，在需要大量匹配元字符时有那么一点用。

### 2.2. Match ###

Match对象是一次匹配的结果，包含了很多关于此次匹配的信息，可以使用Match提供的可读属性或方法来获取这些信息。

属性：

1.  string: 匹配时使用的文本。
2.  re: 匹配时使用的Pattern对象。
3.  pos: 文本中正则表达式开始搜索的索引。值与Pattern.match()和Pattern.seach()方法的同名参数相同。
4.  endpos: 文本中正则表达式结束搜索的索引。值与Pattern.match()和Pattern.seach()方法的同名参数相同。
5.  lastindex: 最后一个被捕获的分组在文本中的索引。如果没有被捕获的分组，将为None。
6.  lastgroup: 最后一个被捕获的分组的别名。如果这个分组没有别名或者没有被捕获的分组，将为None。

方法：

1.  group(\[group1, …\]):   
    获得一个或多个分组截获的字符串；指定多个参数时将以元组形式返回。group1可以使用编号也可以使用别名；编号0代表整个匹配的子串；不填写参数时，返回group(0)；没有截获字符串的组返回None；截获了多次的组返回最后一次截获的子串。
2.  groups(\[default\]):   
    以元组形式返回全部分组截获的字符串。相当于调用group(1,2,…last)。default表示没有截获字符串的组以这个值替代，默认为None。
3.  groupdict(\[default\]):   
    返回以有别名的组的别名为键、以该组截获的子串为值的字典，没有别名的组不包含在内。default含义同上。
4.  start(\[group\]):   
    返回指定的组截获的子串在string中的起始索引（子串第一个字符的索引）。group默认值为0。
5.  end(\[group\]):   
    返回指定的组截获的子串在string中的结束索引（子串最后一个字符的索引+1）。group默认值为0。
6.  span(\[group\]):   
    返回(start(group), end(group))。
7.  expand(template):   
    将匹配到的分组代入template中然后返回。template中可以使用\\id或\\g<id>、\\g<name>引用分组，但不能使用编号0。\\id与\\g<id>是等价的；但\\10将被认为是第10个分组，如果你想表达\\1之后是字符'0'，只能使用\\g<1>0。

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      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(255,20,147);">print</code>&nbsp; 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">"m.endpos:"</code> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">, m.endpos</code> 
     </div> 
     <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(255,20,147);">print</code>&nbsp; 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">"m.lastindex:"</code> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">, m.lastindex</code> 
     </div> 
     <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(255,20,147);">print</code>&nbsp; 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">"m.lastgroup:"</code> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">, m.lastgroup</code> 
     </div> 
     <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;">
       &nbsp; 
     </div> 
     <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(255,20,147);">print</code>&nbsp; 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">"m.group(1,2):"</code> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">, m.group(</code> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,153,0);">1</code> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">, </code> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,153,0);">2</code> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">)</code> 
     </div> 
     <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(255,20,147);">print</code>&nbsp; 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">"m.groups():"</code> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">, m.groups()</code> 
     </div> 
     <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(255,20,147);">print</code>&nbsp; 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">"m.groupdict():"</code> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">, m.groupdict()</code> 
     </div> 
     <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(255,20,147);">print</code>&nbsp; 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">"m.start(2):"</code> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">, m.start(</code> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,153,0);">2</code> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">)</code> 
     </div> 
     <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(255,20,147);">print</code>&nbsp; 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">"m.end(2):"</code> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">, m.end(</code> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,153,0);">2</code> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">)</code> 
     </div> 
     <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(255,20,147);">print</code>&nbsp; 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">"m.span(2):"</code> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">, m.span(</code> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,153,0);">2</code> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">)</code> 
     </div> 
     <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(255,20,147);">print</code>&nbsp; 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">r</code> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">"m.expand(r'\2 \1\3'):"</code> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">, m.expand(r</code> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">'\2 \1\3'</code> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">)</code> 
     </div> 
     <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;">
       &nbsp; 
     </div> 
     <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);">### output ###</code> 
     </div> 
     <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);"># m.string: hello world!</code> 
     </div> 
     <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);"># m.re: &lt;_sre.SRE_Pattern object at 0x016E1A38&gt;</code> 
     </div> 
     <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);"># m.pos: 0</code> 
     </div> 
     <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);"># m.endpos: 12</code> 
     </div> 
     <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);"># m.lastindex: 3</code> 
     </div> 
     <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);"># m.lastgroup: sign</code> 
     </div> 
     <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);"># m.group(1,2): ('hello', 'world')</code> 
     </div> 
     <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);"># m.groups(): ('hello', 'world', '!')</code> 
     </div> 
     <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);"># m.groupdict(): {'sign': '!'}</code> 
     </div> 
     <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);"># m.start(2): 6</code> 
     </div> 
     <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);"># m.end(2): 11</code> 
     </div> 
     <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);"># m.span(2): (6, 11)</code> 
     </div> 
     <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
      <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);"># m.expand(r'\2 \1\3'): world hello!</code> 
     </div> 
    </div></td> 
  </tr> 
 </tbody> 
</table>

### 2.3. Pattern ###

Pattern对象是一个编译好的正则表达式，通过Pattern提供的一系列方法可以对文本进行匹配查找。

Pattern不能直接实例化，必须使用re.compile()进行构造。

Pattern提供了几个可读属性用于获取表达式的相关信息：

1.  pattern: 编译时用的表达式字符串。
2.  flags: 编译时用的匹配模式。数字形式。
3.  groups: 表达式中分组的数量。
4.  groupindex: 以表达式中有别名的组的别名为键、以该组对应的编号为值的字典，没有别名的组不包含在内。

实例方法\[ | re模块方法\]：

1.  match(string\[, pos\[, endpos\]\]) | re.match(pattern, string\[, flags\]):   
    这个方法将从string的pos下标处起尝试匹配pattern；如果pattern结束时仍可匹配，则返回一个Match对象；如果匹配过程中pattern无法匹配，或者匹配未结束就已到达endpos，则返回None。   
    pos和endpos的默认值分别为0和len(string)；re.match()无法指定这两个参数，参数flags用于编译pattern时指定匹配模式。   
    注意：这个方法并不是完全匹配。当pattern结束时若string还有剩余字符，仍然视为成功。想要完全匹配，可以在表达式末尾加上边界匹配符'$'。   
    示例参见2.1小节。
2.  search(string\[, pos\[, endpos\]\]) | re.search(pattern, string\[, flags\]):   
    这个方法用于查找字符串中可以匹配成功的子串。从string的pos下标处起尝试匹配pattern，如果pattern结束时仍可匹配，则返回一个Match对象；若无法匹配，则将pos加1后重新尝试匹配；直到pos=endpos时仍无法匹配则返回None。   
    pos和endpos的默认值分别为0和len(string))；re.search()无法指定这两个参数，参数flags用于编译pattern时指定匹配模式。   
    
    
    <table style="border-spacing:0px;border:1px solid #C0C0C0;background:none;line-height:1.1em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:12px;min-height:auto;"> 
     <tbody style="background:none;line-height:1.1em;vertical-align:baseline;min-height:auto;"> 
      <tr style="background:none;border-top:0px;line-height:1.1em;vertical-align:baseline;min-height:auto;"> 
       <td style="border-color:#C0C0C0;border-collapse:collapse;background:none;line-height:1.1em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:12px;min-height:auto;color:rgb(175,175,175);"> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          1 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          2 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          3 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          4 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          5 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          6 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          7 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          8 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          9 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          10 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          11 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          12 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          13 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          14 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          15 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          16 
        </div></td> 
       <td style="border-color:#C0C0C0;border-collapse:collapse;background:none;line-height:1.1em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:12px;min-height:auto;"> 
        <div style="background:none;border:0px;line-height:1.1em;vertical-align:baseline;min-height:auto;"> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);"># encoding: UTF-8 </code> 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,255);">import</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">re </code> 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;">
           &nbsp; 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);"># 将正则表达式编译成Pattern对象 </code> 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">pattern </code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,255);">=</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">re.</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(255,20,147);">compile</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">(r</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">'world'</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">) </code> 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;">
           &nbsp; 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);"># 使用search()查找匹配的子串，不存在能匹配的子串时将返回None </code> 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);"># 这个例子中使用match()无法成功匹配 </code> 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">match </code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,255);">=</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">pattern.search(</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">'hello world!'</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">) </code> 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;">
           &nbsp; 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,255);">if</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">match: </code> 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;">&nbsp;&nbsp;&nbsp;&nbsp;</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);"># 使用Match获得分组信息 </code> 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;">&nbsp;&nbsp;&nbsp;&nbsp;</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(255,20,147);">print</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">match.group() </code> 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;">
           &nbsp; 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);">### 输出 ### </code> 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);"># world</code> 
         </div> 
        </div></td> 
      </tr> 
     </tbody> 
    </table>
3.  split(string\[, maxsplit\]) | re.split(pattern, string\[, maxsplit\]):   
    按照能够匹配的子串将string分割后返回列表。maxsplit用于指定最大分割次数，不指定将全部分割。   
    
    
    <table style="border-spacing:0px;border:1px solid #C0C0C0;background:none;line-height:1.1em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:12px;min-height:auto;"> 
     <tbody style="background:none;line-height:1.1em;vertical-align:baseline;min-height:auto;"> 
      <tr style="background:none;border-top:0px;line-height:1.1em;vertical-align:baseline;min-height:auto;"> 
       <td style="border-color:#C0C0C0;border-collapse:collapse;background:none;line-height:1.1em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:12px;min-height:auto;color:rgb(175,175,175);"> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          1 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          2 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          3 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          4 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          5 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          6 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          7 
        </div></td> 
       <td style="border-color:#C0C0C0;border-collapse:collapse;background:none;line-height:1.1em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:12px;min-height:auto;"> 
        <div style="background:none;border:0px;line-height:1.1em;vertical-align:baseline;min-height:auto;"> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,255);">import</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">re</code> 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;">
           &nbsp; 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">p </code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,255);">=</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">re.</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(255,20,147);">compile</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">(r</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">'\d+'</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">)</code> 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(255,20,147);">print</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">p.split(</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">'one1two2three3four4'</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">)</code> 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;">
           &nbsp; 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);">### output ###</code> 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);"># ['one', 'two', 'three', 'four', '']</code> 
         </div> 
        </div></td> 
      </tr> 
     </tbody> 
    </table>
4.  findall(string\[, pos\[, endpos\]\]) | re.findall(pattern, string\[, flags\]):   
    搜索string，以列表形式返回全部能匹配的子串。   
    
    
    <table style="border-spacing:0px;border:1px solid #C0C0C0;background:none;line-height:1.1em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:12px;min-height:auto;"> 
     <tbody style="background:none;line-height:1.1em;vertical-align:baseline;min-height:auto;"> 
      <tr style="background:none;border-top:0px;line-height:1.1em;vertical-align:baseline;min-height:auto;"> 
       <td style="border-color:#C0C0C0;border-collapse:collapse;background:none;line-height:1.1em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:12px;min-height:auto;color:rgb(175,175,175);"> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          1 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          2 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          3 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          4 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          5 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          6 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          7 
        </div></td> 
       <td style="border-color:#C0C0C0;border-collapse:collapse;background:none;line-height:1.1em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:12px;min-height:auto;"> 
        <div style="background:none;border:0px;line-height:1.1em;vertical-align:baseline;min-height:auto;"> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,255);">import</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">re</code> 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;">
           &nbsp; 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">p </code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,255);">=</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">re.</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(255,20,147);">compile</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">(r</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">'\d+'</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">)</code> 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(255,20,147);">print</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">p.findall(</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">'one1two2three3four4'</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">)</code> 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;">
           &nbsp; 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);">### output ###</code> 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);"># ['1', '2', '3', '4']</code> 
         </div> 
        </div></td> 
      </tr> 
     </tbody> 
    </table>
5.  finditer(string\[, pos\[, endpos\]\]) | re.finditer(pattern, string\[, flags\]):   
    搜索string，返回一个顺序访问每一个匹配结果（Match对象）的迭代器。   
    
    
    <table style="border-spacing:0px;border:1px solid #C0C0C0;background:none;line-height:1.1em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:12px;min-height:auto;"> 
     <tbody style="background:none;line-height:1.1em;vertical-align:baseline;min-height:auto;"> 
      <tr style="background:none;border-top:0px;line-height:1.1em;vertical-align:baseline;min-height:auto;"> 
       <td style="border-color:#C0C0C0;border-collapse:collapse;background:none;line-height:1.1em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:12px;min-height:auto;color:rgb(175,175,175);"> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          1 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          2 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          3 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          4 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          5 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          6 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          7 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          8 
        </div></td> 
       <td style="border-color:#C0C0C0;border-collapse:collapse;background:none;line-height:1.1em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:12px;min-height:auto;"> 
        <div style="background:none;border:0px;line-height:1.1em;vertical-align:baseline;min-height:auto;"> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,255);">import</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">re</code> 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;">
           &nbsp; 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">p </code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,255);">=</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">re.</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(255,20,147);">compile</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">(r</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">'\d+'</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">)</code> 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,255);">for</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">m </code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,255);">in</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">p.finditer(</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">'one1two2three3four4'</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">):</code> 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;">&nbsp;&nbsp;&nbsp;&nbsp;</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(255,20,147);">print</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">m.group(),</code> 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;">
           &nbsp; 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);">### output ###</code> 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);"># 1 2 3 4</code> 
         </div> 
        </div></td> 
      </tr> 
     </tbody> 
    </table>
6.  sub(repl, string\[, count\]) | re.sub(pattern, repl, string\[, count\]):   
    使用repl替换string中每一个匹配的子串后返回替换后的字符串。   
    当repl是一个字符串时，可以使用\\id或\\g<id>、\\g<name>引用分组，但不能使用编号0。   
    当repl是一个方法时，这个方法应当只接受一个参数（Match对象），并返回一个字符串用于替换（返回的字符串中不能再引用分组）。   
    count用于指定最多替换次数，不指定时全部替换。   
    
    
    <table style="border-spacing:0px;border:1px solid #C0C0C0;background:none;line-height:1.1em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:12px;min-height:auto;"> 
     <tbody style="background:none;line-height:1.1em;vertical-align:baseline;min-height:auto;"> 
      <tr style="background:none;border-top:0px;line-height:1.1em;vertical-align:baseline;min-height:auto;"> 
       <td style="border-color:#C0C0C0;border-collapse:collapse;background:none;line-height:1.1em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:12px;min-height:auto;color:rgb(175,175,175);"> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          1 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          2 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          3 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          4 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          5 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          6 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          7 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          8 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          9 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          10 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          11 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          12 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          13 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          14 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          15 
        </div></td> 
       <td style="border-color:#C0C0C0;border-collapse:collapse;background:none;line-height:1.1em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:12px;min-height:auto;"> 
        <div style="background:none;border:0px;line-height:1.1em;vertical-align:baseline;min-height:auto;"> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,255);">import</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">re</code> 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;">
           &nbsp; 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">p </code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,255);">=</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">re.</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(255,20,147);">compile</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">(r</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">'(\w+) (\w+)'</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">)</code> 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">s </code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,255);">=</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">'i say, hello world!'</code> 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;">
           &nbsp; 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(255,20,147);">print</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">p.sub(r</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">'\2 \1'</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">, s)</code> 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;">
           &nbsp; 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,255);">def</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">func(m):</code> 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;">&nbsp;&nbsp;&nbsp;&nbsp;</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,255);">return</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">m.group(</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,153,0);">1</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">).title() </code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,255);">+</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">' '</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,255);">+</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">m.group(</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,153,0);">2</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">).title()</code> 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;">
           &nbsp; 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(255,20,147);">print</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">p.sub(func, s)</code> 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;">
           &nbsp; 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);">### output ###</code> 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);"># say i, world hello!</code> 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);"># I Say, Hello World!</code> 
         </div> 
        </div></td> 
      </tr> 
     </tbody> 
    </table>
7.  subn(repl, string\[, count\]) |re.sub(pattern, repl, string\[, count\]):   
    返回 (sub(repl, string\[, count\]), 替换次数)。   
    
    
    <table style="border-spacing:0px;border:1px solid #C0C0C0;background:none;line-height:1.1em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:12px;min-height:auto;"> 
     <tbody style="background:none;line-height:1.1em;vertical-align:baseline;min-height:auto;"> 
      <tr style="background:none;border-top:0px;line-height:1.1em;vertical-align:baseline;min-height:auto;"> 
       <td style="border-color:#C0C0C0;border-collapse:collapse;background:none;line-height:1.1em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:12px;min-height:auto;color:rgb(175,175,175);"> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          1 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          2 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          3 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          4 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          5 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          6 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          7 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          8 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          9 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          10 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          11 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          12 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          13 
        </div> 
        <div style="background-image:none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          14 
        </div> 
        <div style="background:rgb(244,244,244) none;border-width:0px 2px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);line-height:1.8em;text-align:right;vertical-align:baseline;min-height:auto;">
          15 
        </div></td> 
       <td style="border-color:#C0C0C0;border-collapse:collapse;background:none;line-height:1.1em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:12px;min-height:auto;"> 
        <div style="background:none;border:0px;line-height:1.1em;vertical-align:baseline;min-height:auto;"> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,255);">import</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">re</code> 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;">
           &nbsp; 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">p </code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,255);">=</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">re.</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(255,20,147);">compile</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">(r</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">'(\w+) (\w+)'</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">)</code> 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">s </code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,255);">=</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">'i say, hello world!'</code> 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;">
           &nbsp; 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(255,20,147);">print</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">p.subn(r</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">'\2 \1'</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">, s)</code> 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;">
           &nbsp; 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,255);">def</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">func(m):</code> 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;">&nbsp;&nbsp;&nbsp;&nbsp;</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,255);">return</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">m.group(</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,153,0);">1</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">).title() </code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,255);">+</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#0000FF;">' '</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,255);">+</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">m.group(</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,153,0);">2</code> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">).title()</code> 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;">
           &nbsp; 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(255,20,147);">print</code>&nbsp; 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,0,0);">p.subn(func, s)</code> 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;">
           &nbsp; 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);">### output ###</code> 
         </div> 
         <div style="background-image:none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);"># ('say i, world hello!', 2)</code> 
         </div> 
         <div style="background:rgb(244,244,244) none;border:0px;line-height:1.8em;vertical-align:baseline;min-height:auto;"> 
          <code style="background:none;border:0px;line-height:1.8em;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(0,130,0);"># ('I Say, Hello World!', 2)</code> 
         </div> 
        </div></td> 
      </tr> 
     </tbody> 
    </table>

以上就是Python对于正则表达式的支持。熟练掌握正则表达式是每一个程序员必须具备的技能，这年头没有不与字符串打交道的程序了。笔者也处于初级阶段，与君共勉，^\_^

另外，图中的特殊构造部分没有举出例子，用到这些的正则表达式是具有一定难度的。有兴趣可以思考一下，如何匹配不是以abc开头的单词，^\_^

全文结束

[re_simple]: /images/20220521/c675ee9232d64e85810f024d646a6bab.png
[pyre]: /images/20220521/84c6f62370e345beb9802bcc6ee4ca6f.png