边界字符的使用

import re
# 匹配 qq 邮箱，5-10 位数字
qq = '8782303@qq.com'
# <re.Match object; span=(0, 14), match='8782303@qq.com'>
qq = '8782303@qq.cn' # None
# 必须限制结尾
pattern = r'[1-9]d{4,9}@qq.com$' # 结尾$原生字符串
v = re.match(pattern,qq)
print(v)

print('----------^开始----------')
s = 'hello world'
# s = 'python'  # None
pattern = r'^hello.*'
# <re.Match object; span=(0, 11), match='hello world'>
o = re.match(pattern,s)
print(o)

print('-----------\b匹配单词的左边界----------')
pattern = r'.*ab'
# ab 左边界的情况
v = re.match(pattern,'123 abeer')
print(v)
# <re.Match object; span=(0, 6), match='123 ab'>

print('-------------\b匹配单词的右边界----------')
pattern = r'.*ab'
s = '12345 cab'
o = re.match(pattern,s)
print(o)
# <re.Match object; span=(0, 9), match='12345 cab'>

print('-------------\B匹配非单词的右边界----------')
pattern = r'.*abB'
s = '12345 abc'
o = re.match(pattern,s)
print(o)
# <re.Match object; span=(0, 8), match='12345 ab'>