python正则表达式1

使用正则表达式，需要导入re这个模块

>>> import re
>>> pattern=r'abc'
>>> str='abcdefghijabc11111abc'
>>> re.findall( pattern, str )
['abc', 'abc', 'abc']
>>> 

r定义正则表达式的规则，这里匹配abc这个字符串

元字符（[]）匹配一个范围

>>> str="abc afc awc"
>>> pattern=r"a[bfw]c"
>>> re.findall( pattern, str )
['abc', 'afc', 'awc']
>>> pattern=r"a[bf]w"
>>> re.findall( pattern, str )
[]
>>> pattern=r"a[bf]c"
>>> re.findall( pattern, str )
['abc', 'afc']
>>> 

^：以...开头，用在中括号里面表示非(取反，或者说排除)

>>> import re
>>> str="ghostwu:hi my name is ghostwu, nice to meet you!"
>>> pattern=r"ghostwu"
>>> re.findall( pattern, str )
['ghostwu', 'ghostwu']
>>> pattern=r"^ghostwu"
>>> re.findall( pattern, str )
['ghostwu']
>>> 

>>> str="abc"
>>> pattern=r"a[b]c"
>>> re.findall( pattern, str )
['abc']
>>> pattern=r"a[^b]c"
>>> re.findall( pattern, str )
[]
>>> 

$:以....结尾

>>> str="ghostwu:hi my name is ghostwu, nice to meet you! Hanmeimei: Hi,ghostwu"
>>> pattern=r"ghostwu"
>>> re.findall( pattern, str )
['ghostwu', 'ghostwu', 'ghostwu']
>>> pattern=r"ghostwu$"
>>> re.findall( pattern, str )
['ghostwu']
>>> 

$在中括号中被当做普通的字符串匹配

>>> pattern=r"a[bcd$]"
>>> re.findall( pattern, 'ab' )
['ab']
>>> re.findall( pattern, 'ac' )
['ac']
>>> re.findall( pattern, 'ad' )
['ad']
>>> re.findall( pattern, 'abe' )
['ab']
>>> re.findall( pattern, 'a$' )
['a$']
>>> 

转义字符 \

>>> str="^ghostwu ^ghostwu ^ghostwu"
>>> pattern=r"^ghostwu"
>>> re.findall( pattern, str )
[]
>>> pattern=r"ghostwu"
>>> re.findall( pattern, str )
['ghostwu', 'ghostwu', 'ghostwu']
>>> pattern=r"\^ghostwu"
>>> re.findall( pattern, str )
['^ghostwu', '^ghostwu', '^ghostwu']
>>>