择一匹配符和数据集列表

# 列表（[]）和 择一匹配符（|）完成相同的效果
import re

m = re.match('[xzy]','x')
print(m.group())
m = re.match('x|y|z','x')
print(m.group())

# 字符集列表与择一匹配符的用法，及差异
pattern = r'[ab][cd]'
# 匹配第一个字母是a或b,第一个字母是c或d
s = 'ac' 
# <re.Match object; span=(0, 2), match='ac'>
s = 'ab'
# None
m = re.match(pattern,s)
print(m)

pattern = r'ab[cd]'
# 以ab开头,后面以c或d开头
s = 'ab' # None
s = 'abc' 
# <re.Match object; span=(0, 3), match='abc'>
s = 'abd'
# <re.Match object; span=(0, 3), match='abd'>
m = re.match(pattern,s)
print(m)

pattern = 'ab|cd'
s = 'abc'
# <re.Match object; span=(0, 2), match='ab'>
s = 'abd'
# <re.Match object; span=(0, 2), match='ab'>
s = 'cd'
# <re.Match object; span=(0, 2), match='cd'>
m = re.match(pattern,s)
print(m)