Python 正则表达式

1、常见正则表达式符号和特殊字符

2、常见正则表达式属性

3、re模块函数的使用

match() 方法匹配字符串

# 需要导入 re 模块>>> import re>>> m = re.match('fo', 'foo')>>> m<_sre.SRE_Match object; span=(0, 2), match='fo'>>>> m.group()'fo'# 如果匹配失败， 将会抛出 AttributeError 异常# 可以用 if m is not None： m.group() 先判断是否为 None>>> m = re.match('fo', 'ofo ofo ')>>> m>>> m.group()Traceback (most recent call last):  File "<pyshell#8>", line 1, in <module>    m.group()AttributeError: 'NoneType' object has no attribute 'group'# 模式匹配只能从字符串的起始部分开始， 即使字符串更长，匹配也能成功>>> m = re.match('fo', 'fo 0000, lll')>>> m.group()'fo'

search() 方法匹配字符串

# search 函数会搜索在字符串中第一次出现的位置，并且从左向右搜索>>> m = re.search('fo', 'we foo iiie foo')>>> m<_sre.SRE_Match object; span=(3, 5), match='fo'>

匹配多个字符

>>> bt = 'bat|bct|bbt'>>> s = re.search(bt, 'foo bat bct')>>> s.group()'bat'

[]字符集

>>> m = re.match('[cr][23][dp][o2]', 'c3po')>>> m.group()'c3po'

用groups() 子组获得一个包含所有匹配子组的元组

>>> m = re.match('\w\w\w-\d\d\d', 'abc-123')>>> m.group()'abc-123'>>> m.group(1)Traceback (most recent call last):  File "<pyshell#49>", line 1, in <module>    m.group(1)IndexError: no such group>>> m.group(0)'abc-123'>>> m = re.match('(\w\w\w)-(\d\d\d)', 'abc-123')# m.group() 和 m.group(0) 的效果是一样的 >>> m.group()'abc-123'>>> m.group(1)'abc'>>> m.group(0)'abc-123'>>> m.group(2)'123'>>> m = re.match('ab', 'ab')>>> m.group()'ab'>>> m.groups()()>>> >>> m = re.match('(ab)', 'ab')>>> m.group()'ab'>>> m.group(1)'ab'>>> m.group(0)'ab'>>> m.group(2)Traceback (most recent call last):  File "<pyshell#64>", line 1, in <module>    m.group(2)IndexError: no such group>>> m.groups()('ab',)>>> m = re.match('(a)(b)', 'ab')>>> m.group()'ab'>>> m.group(1)'a'>>> m.group(0)'ab'>>> m.group(2)'b'>>> m.groups()('a', 'b')# groups() 是根据 pattern 由外到内分组的 >>> m = re.match('(a(b))', 'ab')>>> m.group()'ab'>>> m.group(0)'ab'>>> m.group(1)'ab'>>> m.group(2)'b'>>> m.groups()('ab', 'b')>>> m = re.match('(a(b(c)))', 'abc')>>> m.group()'abc'>>> m.group(0)'abc'>>> m.group(1)'abc'>>> m.group(2)'bc'>>> m.group(3)'c'>>> m.groups()('abc', 'bc', 'c')>>> m = re.match('a(b(c(d)))', 'abcd')>>> m.group()'abcd'>>> m.group(0)'abcd'>>> m.group(1)'bcd'>>> m.group(2)'cd'>>> m.groups()('bcd', 'cd', 'd')

匹配字符串的起始和结尾以及单词边界

# ^ 用来匹配以 pattern 作为起始的字符串>>> m = re.match('^from', 'from')>>> m.group()'from'>>> m = re.match('^from','fromasdads')>>> m.group()'from'>>> m = re.match('^from', 'd from')>>> m.group()Traceback (most recent call last):  File "<pyshell#129>", line 1, in <module>    m.group()AttributeError: 'NoneType' object has no attribute 'group'# $ 用来匹配以 pattern 作为结尾的字符串, 测试了很多都是报错， 不知# 道什么鬼>>> m = re.match('/bin/tcsh$', '/bin/tcsh')>>> m.group()'/bin/tcsh'>>> m = re.match('ad$', 'ad adadad')>>> m.group()Traceback (most recent call last):  File "<pyshell#122>", line 1, in <module>    m.group()AttributeError: 'NoneType' object has no attribute 'group'>>> m = re.group('ad$', 'ad ad ad')Traceback (most recent call last):  File "<pyshell#123>", line 1, in <module>    m = re.group('ad$', 'ad ad ad')AttributeError: module 're' has no attribute 'group'>>> m = re.match('ad$', 'ad ad ad')>>> m.group()Traceback (most recent call last):  File "<pyshell#125>", line 1, in <module>    m.group()AttributeError: 'NoneType' object has no attribute 'group'>>> m = re.match('bin$', 'aa bin')>>> m.group()Traceback (most recent call last):  File "<pyshell#131>", line 1, in <module>    m.group()AttributeError: 'NoneType' object has no attribute 'group'# 后来才发现要用search() 函数>>> s = re.search('/bin/bac$', 'dada/bin/bac')>>> s.group()'/bin/bac'# ^ 和 $ 组合，pattern 匹配单独构成的字符串>>> m = re.match('^bin$', 'bin')>>> m.group()'bin'>>> m = re.match('^bin$', 'bin bin')>>> m.group()Traceback (most recent call last):  File "<pyshell#138>", line 1, in <module>    m.group()AttributeError: 'NoneType' object has no attribute 'group'>>> m.group()'the'# \b 匹配边界   \B 匹配不以 pattern 为边界的字符串>>> m = re.match(r'\bhte', 'thr the thr')>>> m.group()Traceback (most recent call last):  File "<pyshell#151>", line 1, in <module>    m.group()AttributeError: 'NoneType' object has no attribute 'group'>>> m = re.match(r'\Bthe', 'thr the thr')>>> m.group()Traceback (most recent call last):  File "<pyshell#153>", line 1, in <module>    m.group()AttributeError: 'NoneType' object has no attribute 'group'>>> m = re.match(r'\Bthe', 'thenthethe')>>> m.group()Traceback (most recent call last):  File "<pyshell#155>", line 1, in <module>    m.group()AttributeError: 'NoneType' object has no attribute 'group'>>> m = re.group(r'\Bthe', 'thithe')Traceback (most recent call last):  File "<pyshell#156>", line 1, in <module>    m = re.group(r'\Bthe', 'thithe')AttributeError: module 're' has no attribute 'group'>>> m = re.match('r\Bthe', 'thithe')>>> m.group()Traceback (most recent call last):  File "<pyshell#158>", line 1, in <module>    m.group()AttributeError: 'NoneType' object has no attribute 'group'>>> m = re.match(r'\Bthe', 'banbinthe')>>> m.group()Traceback (most recent call last):  File "<pyshell#161>", line 1, in <module>    m.group()AttributeError: 'NoneType' object has no attribute 'group'>>> m = re.match(r'\Bthe', 'the theathe')>>> s = re.search(r'\Bthe', 'the thathe')>>> s.group()'the'>>> s = re.search('/bin/bac$', 'dada/bin/bac')>>> s.group()'/bin/bac'>>> m = re.match(r'\Bthe', 'the theathe')>>> s = re.search(r'\Bthe', 'the thathe')>>> s.group()'the'>>> s = re.search(r'\bthe', 'thr the tha')>>> s.group()'the'

findall() 与 finditer()

# findall()  查询字符串中符合 pattern 的全部非重复出现情况，返回列表>>> re.findall('car', 'carry the barcardi to the car')['car', 'car', 'car']# finditer()  比 findall() 节省内存并在匹配对象中迭代>>> for i in re.finditer(r'\d+', '2 2663 887 322'):    print(i.group())    22663887322

sub() 和 subn()

# subn() 和 sub() 几乎一样， subn() 还可以返回一个表示替换的总数>>> re.sub('[abc]', '789', 'aadhkahdkankdkdnlanl')'789789dhk789hdk789nkdkdnl789nl'>>> re.subn('[abc]', '789', 'adadadaddq3 euduashbfiau')('789d789d789d789ddq3 eudu789sh789fi789u', 7)

split() 分隔字符串

>>> re.split(':', 'str1:str2:str3')['str1', 'str2', 'str3']