Python-基础(7) Regular Expressions

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Regular Expressions

在正则表达式中的字符：

  • Non-special chars match themselves. 非特殊字符，匹配字符自身
  • Exceptions are special characters. 特殊字符不是匹配自身，而是按照如下特殊字符匹配规则匹配

特殊字符匹配规则：

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\       Escape special char or start a sequence.转义字符，用于停止特殊字符匹配功能
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.       Match any char except newline, see re.DOTALL 匹配所有字符（不包括换行符）
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^       Match start of the string, see re.MULTILINE 匹配行开始
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$       Match end of the string, see re.MULTILINE 匹配行结束
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[]      Enclose a set of matchable chars 列举
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R|S     Match either regex R or regex S.  【|】或
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()      Create capture group, & indicate precedence     分组符
After '[', enclose a set, the only special chars are:
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]   End the set, if not the first char
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-   A range, eg. a-c matches a, b or c   表范围
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^   Negate the set only if it is the 1st char 否定

Regular Expression Examples

re.findall()

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# split all string from a sentence
>>> import re
>>> source = "Python is great!"
>>> re.findall('[\w]+', source)   #\w 匹配所有字母
['Python', 'is', 'great!']

Match hex color value

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>>> re.match('^#?([a-f0-9]{6}|[a-f0-9]{3})$', '#ffffff')
<_sre.SRE_Match object at 0x0000000002F04120>
>>> re.match('^#?([a-f0-9]{6}|[a-f0-9]{3})$', '#cdcdcd')
<_sre.SRE_Match object at 0x0000000002EA3160>

Match username doesn’t have any special characters

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>>> re.match('^[a-zA-Z0-9-_]{3,16}$', 'Check') is not None
True
>>> re.match('^\w|[-_]{3,16}$', 'che%ck') is not None
False

Match email address format

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re.match('^([a-z0-9_\.-]+)@([\da-z\.-]+)\.([a-z\.]{2,6})$',
...          'check@example.com')
<_sre.SRE_Match object at 0x0000000002EA3180>