regex error - nothing to repeat

user_357236 0
Viewed 171980

I get an error message when I use this expression:

re.sub(r"([^\s\w])(\s*\1)+","\\1","...")

I checked the regex at RegExr and it returns . as expected. But when I try it in Python I get this error message:

raise error, v # invalid expression
sre_constants.error: nothing to repeat

Can someone please explain?

python regex
6 Answers

regular expression normally uses * and + in theory of language. I encounter the same bug while executing the line code 

re.split("*",text)

to solve it, it needs to include \ before * and +

re.split("\*",text)
user_12917770

Beyond the bug that was discovered and fixed, I'll just note that the error message sre_constants.error: nothing to repeat is a bit confusing. I was trying to use r'?.*' as a pattern, and thought it was complaining for some strange reason about the *, but the problem is actually that ? is a way of saying "repeat zero or one times". So I needed to say r'\?.*'to match a literal ?

user_5075440

I had this problem when using the regex \b?. Using \s? fixed the issue (although it's not the same thing)

user_17199310
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