表示邊界

示例1：$

需求：匹配163.com的郵箱地址

#coding=utf-8

import re

# 正確的地址
ret = re.match("[\w]{4,20}@163\.com", "[email protected]")
ret.group()

# 不正確的地址
ret = re.match("[\w]{4,20}@163\.com", "[email protected]")
ret.group()

# 通過$來確定末尾
ret = re.match("[\w]{4,20}@163\.com$", "[email protected]")
ret.group()

示例2: \b

>>> re.match(r".*\bver\b", "ho ver abc").group()
'ho ver'

>>> re.match(r".*\bver\b", "ho verabc").group()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'NoneType' object has no attribute 'group'

>>> re.match(r".*\bver\b", "hover abc").group()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'NoneType' object has no attribute 'group'

示例3：\B

>>> re.match(r".*\Bver\B", "hoverabc").group()
'hover'

>>> re.match(r".*\Bver\B", "ho verabc").group()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'NoneType' object has no attribute 'group'

>>> re.match(r".*\Bver\B", "hover abc").group()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'NoneType' object has no attribute 'group'

>>> re.match(r".*\Bver\B", "ho ver abc").group()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'NoneType' object has no attribute 'group'

匹配分組

示例1：|

需求：匹配出0-100之間的數字

#coding=utf-8

import re

ret = re.match("[1-9]?\d","8")
ret.group()

ret = re.match("[1-9]?\d","78")
ret.group()

# 不正確的情況
ret = re.match("[1-9]?\d","08")
ret.group()

# 修正之後的
ret = re.match("[1-9]?\d$","08")
ret.group()

# 添加|
ret = re.match("[1-9]?\d$|100","8")
ret.group()

ret = re.match("[1-9]?\d$|100","78")
ret.group()

ret = re.match("[1-9]?\d$|100","08")
ret.group()

ret = re.match("[1-9]?\d$|100","100")
ret.group()

示例2：( )

需求：匹配出163、126、qq郵箱之間的數字

#coding=utf-8

import re

ret = re.match("\w{4,20}@163\.com", "[email protected]")
ret.group()

ret = re.match("\w{4,20}@(163|126|qq)\.com", "[email protected]")
ret.group()

ret = re.match("\w{4,20}@(163|126|qq)\.com", "[email protected]")
ret.group()

ret = re.match("\w{4,20}@(163|126|qq)\.com", "[email protected]")
ret.group()