Python的正则表达式的模块名字是‘re'
>>> import re
>>> rawString = r'This is a normal string.'
>>> rawString
'This is a normal string.'
>>> string = 'This is a normal string.'
>>> string
'This is a
normal string.'
==================================
>>> match = re.match(r'dog', 'dog cat dog')
>>> match.group(0)
'dog'
.match()函数只能从字符串最开始进行匹配
>>> match = re.match(r'cat', 'dog cat dog')
>>> match
>>>
===================================
.search()函数可以在字符串里从左到右自有匹配，不过只能匹配一次，查找到一个匹配项之后就停止
>>> match = re.search(r'cat', 'dog cat dog')
>>> match.group(0)
'cat'
====================================
.findall()函数可以在字符串里，查找到所有匹配项，并放入一个列表中
>>> match = re.findall(r'dog', 'dog cat dog')
>>> match
['dog', 'dog']
>>> match = re.findall(r'cat', 'dog cat dog')
>>> match
['cat']
=====================================
>>> match = re.search(r'dog', 'dog cat dog')
>>> match.start()
0
>>> match.end()
3
.start()与.end()两个函数，可用于告诉该匹配对象在字符串中的开始位置与结束为止
=====================================
>>> contaciInfo = 'Doe, John: 555-1212'
>>> match = re.search(r'(?P<.last>w+), (?P<first>w+): (?P<phone>S+)', contactInfo)
>>> match.group('last')
'Doe'
>>> match.group('first')
'John'
>>> match.group('phone')
'555-1212'
可以直接给分组命名，方便后续使用。不过.findall()函数不适用于命名
>>> re.findall(r'(w+), (w+): (S+)', contactInfo)
[('Doe', 'John', '555-1212')]
====================================================