学习目的：
正则表达式是对字符串操作的一种逻辑公式，就是用事先定义好的一些特点字符、及这些特点字符组合，组成一个“规则字符串”，这个“规则字符串”用来表达对字符串的一种过滤逻辑。
正式步骤
Step1：常用匹配模式
Step2：最常规的匹配
import re testString = ‘I have 4Learned the python years‘ print(len(testString)) result = re.match(‘^I\s\w{4}\s\d\w{7}.*years$‘,testString) print(result) print(result.group()) #现实匹配结果 print(result.span() #现实匹配区间
运行结果：
32 <_sre.SRE_Match object; span=(0, 32), match=‘I have 4Learned the python years‘> I have 4Learned the python years (0, 32)
范匹配：
.*可以把除了匹配的开头和结尾都匹配
import re testString = ‘I have 4Learned the python years‘ print(len(testString)) result = re.match(‘^I.*years$‘,testString) print(result) print(result.group()) print(result.span())
匹配目标：
设置起始端点后，用()来把需要匹配的目标括号起来
import re testString = ‘I have Learned the python years‘ print(len(testString)) result = re.match(‘^I\s\w{4}\s(\w+)\s.*years$‘,testString) print(result) print(result.group(1)) print(result.span())
贪婪匹配：
import re testString = ‘I have 7777 Learned the python years‘ print(len(testString)) result = re.match(‘^I.*(\d+).*years$‘,testString) print(result) print(result.group(1)) print(result.span())
运行结果：
36 <_sre.SRE_Match object; span=(0, 36), match=‘I have 7777 Learned the python years‘> 7 (0, 36)
非贪婪匹配
import re testString = ‘I have 7777 Learned the python years‘ print(len(testString)) result = re.match(‘^I.*?(\d+).*years$‘,testString) print(result) print(result.group(1)) print(result.span())
运行结果：
36 <_sre.SRE_Match object; span=(0, 36), match=‘I have 7777 Learned the python years‘> 7777 (0, 36)
Step3：匹配模式
包含换行符：
import re testString = ‘‘‘I have 7777 Learned the python years‘‘‘ print(len(testString)) result = re.match(‘^I.*(\d+).*years$‘,testString,re.S) print(result) print(result.group(1)) print(result.span())
转义：
import re content = "i have $5.00" result = re.match(‘i have \$5\.00‘,content) print(result.group())
Step4: re.search
功能：扫描整个字符串，返回第一个成功的匹配
import re testString = ‘‘‘I have 7777 Learned the python years‘‘‘ print(len(testString)) result = re.search(‘I.*(\d+).*years$‘,testString,re.S) print(result) print(result.group(1)) print(result.span())
总结：为了匹配方便，能用search就不用match，因为search方法不用限制匹配字符串的头部必须一致
学习总结：
正则表达式的应用需要多实践
