第11次预习课-20180905

Posted 2021-01-04 xuefeifei

正则表达式

 

精确匹配或者模糊匹配

比如：匹配所有日志中的ip，匹配所有的响应时间。

 

Re: regular expression

所有的语言使用的正则大同小异

 

Match：（匹配一次）表示从字符串的开头匹配，如果从第一个字符就不能匹配，则匹配失败

 

Search （匹配一次）从任意位置匹配

 

 

>>> print(re.search(r"k","ddkey"))

<_sre.SRE_Match object; span=(2, 3), match=‘k‘>

>>> re.search(r"ke","ddkey")

<_sre.SRE_Match object; span=(2, 4), match=‘ke‘>

>>> re.search(r"d","ddk3ey")

<_sre.SRE_Match object; span=(3, 4), match=‘3‘>

 

 

.group() 将匹配的结果显示出来

>>> re.search(r"d","ddk3ey").group()

‘3‘

 

+加号代表匹配1个或多个符合的，但匹配一次

>>> re.search(r"d+","a1b2c3d4").group()

‘1‘

>>> re.search(r"d+","a1234bcd").group()

‘1234‘

Findall （匹配多次）将所有的匹配的放在列表中

>>> re.findall(r"d+","a1b2c3d4")

[‘1‘, ‘2‘, ‘3‘, ‘4‘]

 

D 表示匹配非数字

>>> re.search(r"D","123a1234bcd").group()

‘a‘

 

w 会将数字和字母都匹配出来

>>> re.search(r"w","123a1234bcd").group()

‘1‘

>>> re.search(r"w+","123a1234bcd").group()

‘123a1234bcd‘

>>> re.search(r"w+","123a1234b cd").group()

‘123a1234b‘

 

W 匹配非数字和字母

>>> re.search(r"W+","[email protected]#[email protected]#%$#cd").group()

‘@#[email protected]#%$#‘

 

s  匹配空格 等

>>> re.search(r"s+","[email protected]#$   $#cd").group()

‘   ‘

>>> re.search(r"2s+3","123a12   [email protected]#$   $#cd").group()

‘2   3‘

 

*表示匹配0个或多个

>>> re.match(r"w*","abc").group()

‘abc‘

 

正则表达式的贪婪性，尽量多匹配

>>> re.match(r"w*","abc").group()

‘abc‘

>>> re.match(r"w*"," abc").group()

‘‘

 

？ 限制贪婪性

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

‘abc‘

>>> re.match(r"w+?","abc").group()

‘a‘

 

 

{} 表示，{a,b} 匹配a到b个

>>> re.match(r"a{3}","aaaaabc").group()

‘aaa‘

>>> re.match(r"a{1,3}","aaaaabc").group()

‘aaa‘

>>> re.match(r"a{1,3}?","aaaaabc").group()

‘a‘

 

 

>>> s ="abc12 33"

>>> if re.search(r"d",s):

...     print("字符串有数字")

... else:

...     print("字符串没有数字")

...

字符串有数字

 

 

 

[a-zA-Z]   [0-9]  方括号是代表匹配或的关系

例子

>>> s = "12345aaaaa"

>>> if re.search(r"[1-9]{5}",s):

...     print("hhhh")

...

Hhhh

 

>>> re.search(r"[1-3|a-d]+","sfwejfasasz12314324").group()

‘a‘

>>> re.search(r"[1-2|3-4]+","sfwejfasasz12314324").group()

‘12314324‘

>>> 

 

？表示0次或1次

>>> re.search(r"1?","1234").group()

‘1‘

>>> re.search(r"1?","fsdfsd").group()

‘‘

>>> 

 

分组

>>> re.search(r"(a)(d+)(c)","a1234321c").group(1)

‘a‘

>>> re.search(r"(a)(d+)(c)","a1234321c").group(2)

‘1234321‘

>>> re.search(r"(a)(d+)(c)","a1234321c").group(3)

‘c‘

>>> re.search(r"(a)(d+)(c)","a1234321c").group(4)

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

IndexError: no such group

 

re.I 忽略大小写

>>> re.search(r"a","3AAA21c",re.I).group()

‘A‘

 

. 匹配除了回车之外的字符（ ）

>>> re.match(r"."," sss").group()

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

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

>>> re.match(r".","sss").group()

‘s‘

>>> re.match(r".",".sss").group()

‘.‘

>>>