Python的re.split()不会删除所有匹配的字符 [英] Python's re.split() not removing all matched characters

问题描述

这真让我发疯.我肯定正则表达式会匹配字符串开头的整个日期范围.但是，当我重新拆分时，8会挂在后面.

This is driving me absolutely nuts. I am positive that the entire date range at the start of the string is being matched by the regex. Yet, when I do re.split, an 8 hangs behind. What's going on here and how can I split on that date range (in some cases it might be at the start and in the middle of the string, hence the split)?

import re
a = "09/05/2018-12/18/2018 Lecture Wednesday 01:30PM - 02:45PM, Room to be Announced"
b = r"([0-9]|\/|-){21}"
print re.split(b, a)

结果

['', '8', ' Lecture Wednesday 01:30PM - 02:45PM, Room to be Announced']

推荐答案

从文档中获取re.split:

如果在模式中使用捕获括号，则模式中所有组的文本也将作为结果列表的一部分返回.

If capturing parentheses are used in pattern, then the text of all groups in the pattern are also returned as part of the resulting list.

您确实有一个捕获组，它匹配的最后一个字符是字符8.这就是返回8的原因.

You do have a capturing group, and the last thing it matches is the character 8. That's why 8 is returned.

您可以改用非捕获组:

>>> b = r"(?:[0-9]|\/|-){21}"
           ^^ note these two characters added
>>> re.split(b, a)
['', ' Lecture Wednesday 01:30PM - 02:45PM, Room to be Announced']

或者您可以将所有选择放在一个字符类中，而根本不需要一个组:

Or you could put all the choices in a single character class, and not need a group at all:

>>> b = r"[-/0-9]{21}"
>>> re.split(b, a)
['', ' Lecture Wednesday 01:30PM - 02:45PM, Room to be Announced']

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