I wish to expand on the discussion on the following question

In a regular expression, match one thing or another, or both

with a new condition that I want to name the groups consistently. Something like this -

((?P<A>A)|(?P<B>B)) | ((?P<A>A)(?P<B>B))

which triggers re.error: redefinition of group name ... in Python.

Additional info in case it helps: In my specific application, A is a date and B is a time. Basically I want to allow users to enter a date, or a time, or a date followed by a time (which is why A?B? would not work for me as I do not want it empty).

The group name feature of regex turns out to be very handy when it comes to parsing the date and/or time info to datetime objects and functionalities. This is why I want to be able to keep naming A A and B B even when the pattern repeats. This makes the accepted solution in the cited discussion not work for me.

Edit: Yes, I agree that repeating a pattern is not a good idea in the first place especially when date and time are already messy.

CodePudding user response：

If you want the possibility to match either one of the groups or both groups without matching an empty string, you can assert a non whitespace char to the right of the current position:

(?=\S)((?P<A>A)?(?P<B>B)?)

See a regex demo.