What is wrong with my regex Pattern to find recurring cycles in Python?

Question

I want to match any string that has a recurring cycle. Like in this data:

3333333333333333333333333333333333333333 / 1 digit cycle(3)
1666666666666666666666666666666666666666 / 1 digit cycle(6)
1428571428571428571428571428571428571428 / 6 digit cycle(142857)
1111111111111111111111111111111111111111 / 1 digit cycle(1)
0909090909090909090909090909090909090909 / 2 digit cycle(09)
0834522467546323545411673445234655345222 / no cycle
0769230769230769230769230769230769230769 / 6 digit cycle(769230)
0714285714285714285714285714285714285714 / 6 digit cycle(714285)
0666666666666666666666666666666666666666 / 1 digit cycle(6)

The pattern I have tried is "([0-9]+?)\1+" which works well in other languages (like VB or text editors). I have stored these strings inside a list named values. So here is my code:

import re

#stuff to get values
pattern = re.compile("([0-9]+?)\1+")
for value in values:
    matchObj = pattern.search(value)
    print(matchObj) #-> None
    matchObj = pattern.findall(value)
    print(matchObj) #-> []

What am I doing wrong? Any hint is appreciated.

Ned Batchelder · Accepted Answer · 2011-12-27 03:31:54Z

5

Add an r prefix:

r"([0-9]+?)\1+"

That will make the backslash a literal backslash instead of escaping the 1.

answered Dec 27, 2011 at 3:31

Ned Batchelder

378k77 gold badges583 silver badges675 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Rafael T Over a year ago

thx. works like a charm. Although I saw that r as prefix in the examples of docs.python.org/library/re.html, I couldn't find the explanation for this

ridgerunner Over a year ago

@Rafael T - Be sure to also check out the: Python Regular Expression HOWTO

Nishutosh Sharma Over a year ago

@RafaelT @NedBatchelder How to match all recurring substrings ? abababqweqweqwe -> aba, qwe ?

Collectives™ on Stack Overflow

What is wrong with my regex Pattern to find recurring cycles in Python?

1 Answer 1

3 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related