Python 正则表达式组

Question

为什么这个正则表达式会打印 ('c',) 和 ()？我认为“([abc])+”===“([abc])([abc])([abc])...”

>>> import re
>>> m = re.match("([abc])+", "abc")
>>> print m.groups()
('c',)
>>> m.groups(0)
('c',)
>>> m = re.match("[abc]+", "abc")
>>> m.groups()
()
>>> m.groups(0)
()

Answer 1

来自有关的文档 groups

Return a tuple containing all the subgroups of the match, from 1 up to however many groups are in the pattern. The default argument is used for groups that did not participate in the match; it defaults to None.

在第一个正则表达式([abc])+中，它匹配字符a或b或c 但只会存储最后一场比赛

([abc])+
<----->
Matches a or b or c
Observe carefully. Capturing groups are surrounding only the character class
So, only one character from the matched character class can be stored in capturing group.

如果您想在捕获组中捕获字符串abc，请使用

([abc]+)

Above will find string composed of a or b or c and will store it in capturing group.

在第二个正则表达式 [abc]+ 中，没有捕获组，因此显示空结果。