1.查找文本中的模式：re.search()
import re text = "you are python" match = re.search('are',text) # 返回'are'第一个字符在text中的位置，注意是从0开始 print(match.start()) # 返回'are'最后一个字符在text中的位置，这里是从1开始 print(match.end())
结果：
4 7
2.编译表达式：compile()
import re text = "you are SB"
# compile()函数会把一个表达式字符串转化为一个RegexObject
regexes = {re.compile(p) for p in ['SB','NB','MB'] } for regex in regexes: if regex.search(text): print('seeking ' + regex.pattern + ' >> match') else: print('seeking ' + regex.pattern + ' >> not match')
结果：
seeking NB >> not match seeking SB >> match seeking MB >> not match
3.多重匹配：findall(), finditer()
findall()函数会返回与模式匹配而不重叠的所有字符串。
import re text = "ab aa ab bb ab ba"
# 把text所有的'ab'组合都匹配出来 print(re.findall('ab',text))
结果：
['ab', 'ab', 'ab']
finditer()会返回一个迭代器
import re text = "ab aa ab bb ab ba" for match in re.finditer('ab',text): s = match.start() e = match.end() print('found {} at {} to {}'.format('"ab"',str(s),str(e)))
结果：
found "ab" at 0 to 2 found "ab" at 6 to 8 found "ab" at 12 to 14
4.模式语法
import re def test_patterns(text,patterns = []): # pattern分别返回patterns各项的的第一个元素，desc分别返回patterns各项的的第二个元素 # 本函数相当于把patterns第一项作为匹配条件来匹配text for pattern,desc in patterns: print('匹配方式：' + pattern, '说明：' + desc) print('文本:' + text) for match in re.finditer(pattern,text): s = match.start() e = match.end() print('found {} at {} to {}, result:{}'.format(pattern,str(s),str(e),(text[s:e])))
执行该函数：
# 匹配所有a开头，后面是1个b的
>>> test_patterns('a ab abb abbb ',[('ab','a followed by b')])
匹配方式：ab 说明：a followed by b 文本:a ab abb abbb found ab at 2 to 4, result:ab found ab at 5 to 7, result:ab found ab at 9 to 11, result:ab >>>
重复
模式中有5中表示重复的方法,现在一一展示：
# * 表示该模式会重复0次或多次（重复0次即意味着它不出现也能被匹配） # 匹配a开头，后面为0个或多个b，也就是只要出现a就能匹配 >>> test_patterns('a ac ab abb abbb ',[('ab*','a followed by zero or more b')]) 匹配方式：ab* 说明：a followed by zero or more b 文本:a ac ab abb abbb found ab* at 0 to 1, result:a found ab* at 2 to 3, result:a found ab* at 5 to 7, result:ab found ab* at 8 to 11, result:abb found ab* at 12 to 16, result:abbb >>>
# + 表示该模式至少出现一次 # 匹配a开头，后面至少有1个b的
>>> test_patterns('a ab abb abbb ',[('ab+','a followed by one or more b')]) 匹配方式：ab+ 说明：a followed by one or more b 文本:a ab abb abbb found ab+ at 2 to 4, result:ab found ab+ at 5 to 8, result:abb found ab+ at 9 to 13, result:abbb >>>
# ? 表示模式出现0次或1次 # 匹配a开头，后面为0个或1个b，也就是只要出现a就能匹配 >>> test_patterns('a ab abb abbb ',[('ab+','a followed by one or more b')]) 匹配方式：ab+ 说明：a followed by one or more b 文本:a ab abb abbb found ab+ at 2 to 4, result:ab found ab+ at 5 to 8, result:abb found ab+ at 9 to 13, result:abbb >>>
# 匹配a开头，后面3个b >>> test_patterns('a ab abb abbb ',[('ab{3}','a followed by three b')])
匹配方式：ab{3} 说明：a followed by three b 文本:a ab abb abbb found ab{3} at 9 to 13, result:abbb >>>
# 匹配a开头，后面2个或3个b >>> test_patterns('a ab abb abbb ',[('ab{2,3}','a followed by two or three b')]) 匹配方式：ab{2,3} 说明：a followed by two or three b 文本:a ab abb abbb found ab{2,3} at 5 to 8, result:abb found ab{2,3} at 9 to 13, result:abbb >>>
字符集
字符集是一组字符，包含可以与模式中相应位置匹配的所有字符，例如[ab]可以匹配a或b。
# 匹配所有a或b >>> test_patterns('abca',[('[ab]','either a or b')]) 匹配方式：[ab] 说明：either a or b 文本:abca found [ab] at 0 to 1, result:a found [ab] at 1 to 2, result:b found [ab] at 3 to 4, result:a >>>
# 匹配a开头，后面是a或b的 >>> test_patterns('a aa ab ac',[('a[ab]','a followed by a or b')]) 匹配方式：a[ab] 说明：a followed by a or b 文本:a aa ab ac found a[ab] at 2 to 4, result:aa found a[ab] at 5 to 7, result:ab >>>
# 匹配a开头，后面是1个或多个a或b的 >>> test_patterns('a aaaaa abbb accc',[('a[ab]+','a followed by 1 or more a or b')]) 匹配方式：a[ab]+ 说明：a followed by 1 or more a or b 文本:a aaaaa abbb accc found a[ab]+ at 2 to 7, result:aaaaa found a[ab]+ at 8 to 12, result:abbb >>>