正则表达式

• 用正则表达式查找文本模式

import re

phoneNumRegex = re.compile(r'\d\d\d-\d\d\d\-\d\d\d\d')
mo = phoneNumRegex.search('My number is 415-555-4242.')
print(mo.group())

用import re 导入正则表达式模块；

用re.compile()函数创建一个Regex对象；

向Regex对象的search()方法传入想查找的字符串。它返回一个Match对象；

调用Match对象的group()方法，返回实际匹配文本的字符串。

• 用正则表达式匹配更多模式
  • 利用括号分组

phoneNumReg = re.compile(r'(\d\d\d)-(\d\d\d-\d\d\d\d)')
mo1 = phoneNumReg.search('My number is 415-555-4222.')
print(mo1.group(1))
print(mo1.group(2))
print(mo1.group(0))
print(mo1.groups())

415
555-4222
415-555-4222
('415', '555-4222')

• • 用管道匹配多个分组

heroRegex = re.compile(r'Batman|Tina Fey')
mo1 = heroRegex.search("Batman and Tina Fey.")
print(mo1.group())

batRegex = re.compile(r'Bat(man|mobile|copter|bat)')
mo = batRegex.search("Batmobile lost a wheel")
print(mo.group())
print(mo.group(1))

• • 用问号实现可选匹配

# 用问号实现可选匹配(匹配这个问号之前的分组零次或一次)
batRegex = re.compile(r'Bat(wo)?man')
mo1 = batRegex.search("The Adventures of Batman")
print(mo1.group())

mo2 = batRegex.search("The Adventures of Batwoman")
print(mo2.group())

phoneRegex = re.compile(r'(\d\d\d-)?\d\d\d-\d\d\d\d')
mo1 = phoneRegex.search("My number is 415-555-4242")
print(mo1.group())
mo2 = phoneRegex.search("My number is 555-4242")
print(mo2.group())

• • 用星号匹配0次或多次

batRegex = re.compile(r"Bat(wo)*man")
mo1 = batRegex.search("The Adventures of Batman")
print(mo1.group())

mo2 = batRegex.search("The Adventures of Batwoman")
print(mo2.group())

mo3 = batRegex.search("The Adventures of Batwowowowoman")
print(mo3.group())

• • 用加号匹配一次或多次

batRegex = re.compile(r"Bat(wo)+man")
mo1 = batRegex.search("The Adventures of Batwoman")
print(mo1.group())

mo2 = batRegex.search("The Adventures of Batwowowowoman")
print(mo2.group())

mo3 = batRegex.search("The Adventures of Batman")
print(mo3==None)

• • 用花括号匹配特定次数

haRegex = re.compile(r'(Ha){3}')
mo1 = haRegex.search("HaHaHa")
print(mo1.group())

mo2 = haRegex.search("Ha")
print(mo2==None)