Python 的 re.split() 没有删除所有匹配的字符

Question

这简直让我抓狂。我确信正则表达式匹配字符串开头的整个日期范围。然而，当我执行 re.split 时，一个 8 卡在后面。这是怎么回事，我如何在该日期范围内拆分(在某些情况下，它可能在字符串的开头和中间，因此拆分)？

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']

Answer 1

来自 re.split 的文档:

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，它最后匹配的是字符 8。这就是返回 8 的原因。

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，根本不需要一个组:

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