Python : Regex, Finding Repetitions on a string

Question

I need to find repetitions in a text string. I already found a very nice elegant solution here from @Tim Pietzcker

I am happy with the solution as is but would like to know whether it's possible to extend it little further such that it would accept a string with whitespaces.

For example "a bcab c" would return [(abc,2)]

I tried using the regex pattern "([^\s]+?)\1+") with no luck. Any help is much appreciated.

Answer 1

You should think about removing " " from the text first. You can do it by regex itself.

>>> def repetitions(s):
...    r = re.compile(r"(.+?)\1+")
...    for match in r.finditer(re.sub(r'\s+',"",s)):
...        yield (match.group(1), len(match.group(0))/len(match.group(1)))
... 

Output.

>>> list(repetitions("a bcab c"))
[('abc', 2)]

If you still want to retain the space in the original text, Try this regex: r"(\s*\S+\s*?\S*?)\1+" . But this has limitations.

>>> def repetitions(s):
...    r = re.compile(r"(\s*\S+\s*?\S*?)\1+")
...    for match in r.finditer(s):
...        yield (match.group(1), len(match.group(0))/len(match.group(1)))
... 

Results:

>>> list(repetitions(" abc abc "))
[(' abc', 2)]
>>> list(repetitions("abc abc "))
[('abc ', 2)]
>>> list(repetitions(" ab c ab c "))
[(' ab c', 2)]
>>> list(repetitions("ab cab c "))
[('ab c', 2)]
>>> list(repetitions("blablabla"))
[('bla', 3)]