python - Regex to remove repeated character pattern in a string

Question

I have a string that may have a repeated character pattern, e.g.

'xyzzyxxyzzyxxyzzyx'

I need to write a regex that would replace such string with its smallest repeated pattern:

'xyzzyxxyzzyxxyzzyx' becomes 'xyzzyx',

'abcbaccbaabcbaccbaabcbaccba' becomes 'abcbaccba'

Answer 1

Use the following:

> re.sub(r'(.+?)1+', r'1', 'xyzzyxxyzzyxxyzzyx')
'xyzzyx'
> re.sub(r'(.+?)1+', r'1', 'abcbaccbaabcbaccbaabcbaccba')
'abcbaccba'
> re.sub(r'(.+?)1+', r'1', 'iiiiiiiiiiiiiiiiii')
'i'

It basically matches a pattern that repeats itself (.+?)1+, and removes everything but the repeating pattern, which is captured in the first group 1. Also note that using a reluctant qualifier here, i.e., +? will make the regex backtrack quite a lot.

DEMO.