Finding the recurring pattern

Question

Let\'s say I have a number with a recurring pattern, i.e. there exists a string of digits that repeat themselves in order to make the number in question. For example, such a

Answer 1

(.+?)\1+

Try this. Grab the capture. See demo.

import re
p = re.compile(ur'(.+?)\1+')
test_str = u"1234123412341234"

re.findall(p, test_str)

Add anchors and flag Multiline if you want the regex to fail on 12341234123123, which should return None.

^(.+?)\1+$

See demo.