Python Regex replace but only if two or more characters precede regex expression

Question

I have a pattern: "two_or_more_characters - zero_or_more_characters" and I want to replace it with "two_or_more_characters", where "-" is a dash.

I created regex for it:

re.sub(r'-[\w(){}\[\],.?! ]+', '', t)

and it works as expected for some cases. For example for t = "red-fox" we will get red. But it does not work as needed for example: t = "r-fox". The result is r but I am looking for way to keep r-fox instead.

If text has more then one dash then we need to remove text only after last dash. For example for t = "r-fox-dog" the result should be r-fox

'r ' is 'r' <space>, which IS 2 or more characters, so in my opinion the replacement is correct here. Perhaps, give us a better explanation of what you want. Do you want to ignore spaces before dash? — Petr Blahos
– Petr Blahos, Commented Dec 12, 2022 at 7:50
@PetrBlahos I edited the body of Q to address your questions Thanks. — illuminato
– illuminato, Commented Dec 12, 2022 at 7:58
@zvone: True enough, I would recommend using rpartition though. But regex will automatically solve the "at least 2 characters" task. — Petr Blahos
– Petr Blahos, Commented Dec 12, 2022 at 7:59

Petr Blahos · Accepted Answer · 2022-12-12 07:58:21Z

2

Use a backref - that's the thing in the () in the regular expression, and \1 to "paste" it. I think this works well enough:

re.sub(r'(.{2,})-.*', r'\1', "ss-fox")

answered Dec 12, 2022 at 7:58

Petr Blahos

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