python 正则之字母匹配

A:匹配字符串的开始
 
：匹配一个单词边界
 
取出a边界单词的个数
>>> len(re.findall(r"a"," ab abc add"))
3
B:匹配非单词边界
 
d:匹配任意一个数字范围【0-9】

>>> re.match(r"d+","123abc")
<_sre.SRE_Match object at 0x000000000202A510>

D:匹配任意一个非数字字符== [^d]

>>> re.match(r"D+","ABC123").group()
'ABC'

s：匹配空白字符 练习

>>> print re.match(r"s"," 13d")

<_sre.SRE_Match object at 0x0000000001F1A510>

S:匹配非空白字符

>>> print re.match(r"S","13d")

<_sre.SRE_Match object at 0x0000000001F1A510>

w:匹配单个字符（数字或字母）

>>> print re.match(r"w","13d")

<_sre.SRE_Match object at 0x0000000001F1A510>

w+:匹配多个字符（数字或字母）

>>> print re.match(r"w+","13d")

<_sre.SRE_Match object at 0x0000000001F1A510>

>>> re.match(r"w+","13d")

<_sre.SRE_Match object at 0x0000000001F1A510>

>>> re.match(r"w+","13d").group()

'13d'

>>> re.match(r"D+","13d").group()

Traceback (most recent call last):

File "<stdin>", line 1, in <module>

AttributeError: 'NoneType' object has no attribute 'group'

W:非单词字符，等价于[^w]