Python Regular Expressions

Quick Reference

import sys
import re
reload(sys)
sys.setdefaultencoding('utf-8')

Match Counts

.         匹配任意字符一次
*         匹配前面的表达式0/n次
+         匹配前面的表达式1/n次
？        匹配前面的表达式0/1次
{m}        匹配前面的表达式m次
{m,n}     匹配前面的表达式m到n次
*？       匹配前面的表达式0次
+？       匹配前面的表达式1次

Common Syntax

re.S    匹配所有的字符
re.I    匹配大小写
re.M    多行匹配
re.match从头开始匹配
re.search全文匹配
\d         匹配所有的数字
\D        匹配所有的非数字
\s        匹配所有的文字
\S        匹配所有的非文本
[]        字符集合，匹配里面的所有表达式，使用|分开

Common Operations

Creating a Regular Expression Object

compile(pattern[, flags])

#Create a pattern object from a string containing a regular expression
Search the Entire Text for Objects Matching the Expression

search(pattern, string[, flags])    
#在字符串中查找，只查找一个

Search for Objects Matching the Expression from the Beginning

match(pattern, string[, flags])    
#在字符串的开始处匹配模式

Split a String

split(pattern, string[, maxsplit=0,flags])    
#根据模式的匹配项来分割字符串

Find All Objects Matching the Expression

findall(pattern, string,flags)    
#列出字符串中模式的所有匹配项
return 数组

Replace a String

sub(pat,repl, string[,count=0,flags])    
#将字符串中所有的pat的匹配项用repl替换

Note: this denotes the end of a string, so adding it denotes the end of a string; therefore, adding it denotes the end of a string, meaning that the matched content must occur at the end of the string.
To match the entire string, also add the start-of-string marker ^

When writing a web crawler, you can use a regular expression to match multiple objects, then use a yield generator while iterating over them. The results can be combined into a dictionary, converted to JSON format with json.dumps(), and finally saved to a local text file.

Regular Expression Syntax for Standard Matching

汉字：[\u4e00-\u9fa5]{0,}
英文和数字：[A-Za-z0-9]+
长度为3-20的所有字符：.{3,20}
Email地址：\w+([-+.]\w+)@\w+([-.]\w+).\w+([-.]\w+)*
域名：[a-zA-Z0-9][-a-zA-Z0-9]{0,62}(/.[a-zA-Z0-9][-a-zA-Z0-9]{0,62})+/.?
InternetURL：[a-zA-z]+://[^\s] 或 ^http://([\w-]+.)+[\w-]+(/[\w-./?%&=])?$
手机号码：^(13[0-9]|14[5|7]|15[0|1|2|3|5|6|7|8|9]|18[0|1|2|3|5|6|7|8|9])\d{8}$
国内电话号码：\d{3}-\d{8}|\d{4}-\d{7}(0511-4405222、021-87888822)
日期格式：^\d{4}-\d{1,2}-\d{1,2}
空白行的正则表达式：\n\s*\r (可以用来删除空白行)
腾讯QQ号：[1-9][0-9]{4,}
IP地址提取：\d+.\d+.\d+.\d+