120 lines
2.7 KiB
Markdown
120 lines
2.7 KiB
Markdown
# 原创
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： Python正则表达式（一）
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# Python正则表达式（一）
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# 正则表达式
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>
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参考：[正则表达式](https://github.com/CyC2018/Interview-Notebook/blob/master/notes/%E6%AD%A3%E5%88%99%E8%A1%A8%E8%BE%BE%E5%BC%8F.md)
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## 一、概述
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## 二、匹配单个字符
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```
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# 正则表达式
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nam.
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# 匹配结果
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My name is DS中的name
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```
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## 三、匹配一组字符串
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```
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abcd
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abc1
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abc2
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# 匹配到了abcd
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```
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## 四、使用元字符
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### 匹配空白字符
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<th align="center">元字符</th><th align="center">说明</th>
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|------
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<td align="center">[\b]</td><td align="center">回退（删除一个字符）</td>
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<td align="center">\f</td><td align="center">换页符</td>
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<td align="center">\n</td><td align="center">换行符</td>
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<td align="center">\r</td><td align="center">回车符</td>
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<td align="center">\t</td><td align="center">制表符</td>
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<td align="center">\v</td><td align="center">垂直制表符</td>
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### 匹配特定的字符类别
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#### 数字元字符
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<th align="center">元字符</th><th align="center">说明</th>
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|------
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<td align="center">\d</td><td align="center">数字字符，等价于[0-9]</td>
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<td align="center">\D</td><td align="center">非数字字符，等价于[^0-9]</td>
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#### 字母数字元字符
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<th align="center">元字符</th><th align="center">说明</th>
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|------
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<td align="center">\w</td><td align="center">大小写字母，下划线和数字，等价于[a-zA-Z0-9]</td>
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<td align="center">\W</td><td align="center">对\w取非</td>
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#### 空白字符元字符
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<th align="center">元字符</th><th align="center">说明</th>
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|------
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<td align="center">\s</td><td align="center">任何一个空白字符，等价于[\f\n\r\t\v]</td>
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<td align="center">\S</td><td align="center">对\s取非</td>
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## 五、重复匹配
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```
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[\w.]+@\w+\.\w+
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[\w.]+@[\w]+[\.][\w]+
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```
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## 六、位置匹配
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### 单词边界
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### 字符串边界
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## 七、使用子表达式
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```
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192.168.0.1
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00.00.00.00
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555.555.555.555
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```
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匹配到了第一个
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## 八、回溯引用
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```
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<h1>x</h1>
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<h2>x</h2>
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<h3>x</h1>
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匹配到了前面两个
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```
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<th align="center">元字符</th><th align="center">说明</th>
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|------
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<td align="center">\l</td><td align="center">把下个字符转换成小写</td>
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<td align="center">\u</td><td align="center">把下个字符转换成大写</td>
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<td align="center">\L</td><td align="center">把\L和\E之间的字符全部转换成小写</td>
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<td align="center">\U</td><td align="center">把\U和\E之间的字符全部转换成大写</td>
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<td align="center">\E</td><td align="center">结束\L或者\U</td>
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## 九、前后查找
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## 十、嵌入条件
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### 回溯引用条件
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### 前后查找条件
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