Python Basic Learning Regular Expression 2 (use)

~ Using regular Expressions

- The RE module provides an interface to the regular expression engine that allows you to compile restring into objects and use them for matching.

#如果经常使用, it is recommended to compile compile

Example:

>>> r1=r ' ^\d{3,4}-?\d{8} ' >>> Re.findall (R1, ' 010-12345678 ') [' 010-12345678 ']>>> p_tel= Re.compile (R1) #正则编译, becomes an object, using the Complie method in the RE module to compile;>>> R1 to the compiler. Sre_pattern object at 0x7f2e016173d0> #正则对象 >>> p_tel.findall (' 01035689125 ') [' 01035689125 ']

#编译的正则比未编译的正则效率高

----------------------------------------------------------------------------------------------------------

-re.compile () also accepts an optional Flag Parameters , focus on re. I

-Used to implement different special functions and grammatical changes

Example:

>>> csvt_re=re.compile (R ' CSVT ', re. I) #在编译过程中, add the regular attribute re. I (case insensitive) >>> csvt_re.findall (' csvtcsvt ') [' csvt ', ' CSVT ']

#注意: Add ' r ' to the string before the backslash will not be processed in any special way

----------------------------------------------------------------------------------------------------------

To perform a match:

-The ' Regexobject ' instance has some methods and properties, and the complete list is available in the Python Library Reference

<

Method/Property	Role
Match ()	Determines if re is matched at the beginning of the string
Search ()	Scan the string to find the location of the re match
FindAll ()	Find all the substrings that the re matches and return it as a list
Finditer ()	Find all the substrings that the re matches and return it as an iterator

If no match is reached, match () and search will return none

If successful, a ' Matchobject ' instance is returned.

Example:

Use match

>>> csvt_re=re.compile (R ' CSVT ', re. I) >>> csvt_re.match (' csvt hello ') <_sre. Sre_match object at 0x7f2e01620920> #匹配成功. return macthobject>>> csvt_re.match (' hello ') #匹配失败, return empty >>> csvt_re.match (' Hello csvt ') #返回为空, Note that match matches the position where the string starts

If you use Search

>>> csvt_re.search (' Hello csvt ') <_sre. Sre_match object at 0x7f2e01620988>>>> csvt_re.search (' Hello csvt ') <_sre. Sre_match object at 0x7f2e01620920> #注意此处为不区分大小写 and full table scan

Using FindAll

>>> csvt_re.findall (' Hello csvt hello csvt csvt ') [' csvt ', ' csvt ', ' CSVT '] #返回为列表

Using Finditer

>>> csvt_re.finditer (' Hello csvt hello csvt csvt ') <callable-iterator object at 0x7f2e01634350># Object returned as iterator >>> csvt_re.findall (' CSVT ') [' CSVT ']

Match () Matchobject instance method

Method/Property	Role
Group ()	Returns the string that is matched by the RE
Start ()	Returns the position where the match started
End ()	Returns the position where the match ended
Span ()	Returns a tuple containing the location of a match (start, end)

Group (): return Object

>>> csvt_re=re.compile (R ' CSVT ', re. I) >>> x =csvt_re.match (' Csvt,hello ') >>> x<_sre. Sre_match object at 0x7fa4f527f920>>>> x.group () ' CSVT '

----------------------------------------------------------------------------------------------------------

-Module-level functions

The-re module also provides top-level function calls to match (), search (), subn (), Split (), FindAll (), etc.

Sub, SUBN: Regular replacement

Example:

#单纯的字符串替换 >>> kong = ' Hello Nihao ' >>> kong.replace (' Nihao ', ' word ') ' Hello word ' #使用正则 >>> rs = r ' N...O ' >>> kong = ' Hello Nihao naabo nccco ' >>> re.sub (RS, ' BBB ', Kong) ' Hello BBB bbb bbb ' #匹配替换所有 >> > re.subn (RS, ' BBB ', Kong) (' Hello bbb bbb BBB ', 3) difference between #sub and subn, replacement count

Split (): Regular cut

#字符切割 >>> ip = ' 1.2.3.4 ' >>> ip.split ('. ') [' 1 ', ' 2 ', ' 3 ', ' 4 ']>>> s = ' 123+456-789*000 ' >>> re.split (R ' [\+\-\*\/] ', s) [' 123 ', ' 456 ', ' 789 ', ' 000 ']

#查看更多正则函数:
>>> Dir (re)

#查看帮助:

Help (Re.error)

This article from "thinking More than technology" blog, declined reprint!

Python Basic Learning Regular Expression 2 (use)