Python Crawler _ Regular expression

A logical way to manipulate strings, a filtering logic for strings.
Complete expression: http://tool.oschina.net/uploads/apidocs/jquery/regexp.html

1.

1. Re.match ==> tries to match a pattern from the starting position of the string, and if the first character does not match, the        re.match (pattern,sring,flags=0) does not match properly.

2. Match target:

Import re        content='Hello 1234567 World_this is a regex demo'        result= Re.match ('^hello\s (\d+) \sworld.*demo$', content)    # Regular Expression        Print(Result.group (1))    # outputs the contents        of the first parenthesis Print (Result.span ())     # number of output output strings

3. Greedy match:

 import   re content  ="  hello 1234567 World_this is a regex demo  "   result  =re.match ( " ^he.* (\d+) \sworld.*demo$   " ,content)  print     (Result.group (1)) #   

 #   non-greedy match   Import   re content  = " hello 1234567 World_this is a regex demo  "   result  =re.match ("  ^he.*? ( \d+). *demo$   " ,content)  print  (Result.group (1)) #   output 1234567  

# matching mode:        Import re        content=''Hello 1234567 world_this is         a regex demo        '         result=re.match ('^he.*? ( \d+). *?demo$', content,re.s)    #RE.S is the print that matches the line break        ( Result.group (1))    # output 1234567

4. Escape: Special characters need to be escaped

Import re        content='Price is $'        result=re.match ('  Price is \$500\ ', content)     #转义之后才能匹配

5. Re.search: Scan string, return the first matching character, use Search to not match

Import re        content='Hello 1234567 World_this is a regex demo'        result= Re.search ('hello\s (\d+) \sworld.*demo$', content)     # Output all strings 

6. Re.findall

Results=re.findall (' Regular expression ', Html,re. S)        for in  results:        print(result)        Print (result[1],result[2] ...)

7. Re.sub: String substitution

Import re        content='Hello 1234567 World_this is a regex demo extra stings'         Content=re.sub ('\d+',', content)

8. Re.compile: Compiling strings into regular expressions

Import re        content=''Hello 1234567 world_this is         a regex demo        '         Result=re.compile ('hello.*demo', re.s)    #Re.s is a match line break         Result=re.match (pattern,content)

#实战练习:ImportRequestsImportRE Content=requests.get ('http://book.doubancom/'). Text Patten=re.compile ('<li,*cover.*?href= "(. *?)". *?title= "(. *?)". *?more-meta.*?author> (. *?) </span>.*?year> (. *?) </span>.*?</li>', Re. S) Results=Re.findall (pattern.content)#Print (results)         forResultinchresults URL, name,author,date=Result author=re.sub ('\s',"', author) date=re.sub ('\s',"', date)Print(url,name,author,date)

Python Crawler _ Regular expression