Python/Regex - Match .#,#. in String

Question

What regex can I use to match ".#,#." within a string. It may or may not exist in the string. Some examples with expected outputs might be:

Test1.0,0.csv      -> ('Test1', '0,0', 'csv')         (Basic Example)
Test2.wma          -> ('Test2', 'wma')                (No Match)
Test3.1100,456.jpg -> ('Test3', '1100,456', 'jpg')    (Basic with Large Number)
T.E.S.T.4.5,6.png  -> ('T.E.S.T.4', '5,6', 'png')     (Doesn't strip all periods)
Test5,7,8.sss      -> ('Test5,7,8', 'sss')            (No Match)
Test6.2,3,4.png    -> ('Test6.2,3,4', 'png')          (No Match, to many commas)
Test7.5,6.7,8.test -> ('Test7', '5,6', '7,8', 'test') (Double Match?)

The last one isn't too important and I would only expect that .#,#. would appear once. Most files I'm processing, I would expect to fall into the first through fourth examples, so I'm most interested in those.

Thanks for the help!

Answer 1

You can use the regex \.\d+,\d+\. to find all matches for that pattern, but you will need to do a little extra to get the output you expect, especially since you want to treat .5,6.7,8. as two matches.

Here is one potential solution:

def transform(s):
    s = re.sub(r'(\.\d+,\d+)+\.', lambda m: m.group(0).replace('.', '\n'), s)
    return tuple(s.split('\n'))

Examples:

>>> transform('Test1.0,0.csv')
('Test1', '0,0', 'csv')
>>> transform('Test2.wma')
('Test2.wma',)
>>> transform('Test3.1100,456.jpg')
('Test3', '1100,456', 'jpg')
>>> transform('T.E.S.T.4.5,6.png')
('T.E.S.T.4', '5,6', 'png')
>>> transform('Test5,7,8.sss')
('Test5,7,8.sss',)
>>> transform('Test6.2,3,4.png')
('Test6.2,3,4.png',)
>>> transform('Test7.5,6.7,8.test')
('Test7', '5,6', '7,8', 'test')

To also get the file extension split off when there are no matches, you can use the following:

def transform(s):
    s = re.sub(r'(\.\d+,\d+)+\.', lambda m: m.group(0).replace('.', '\n'), s)
    groups = s.split('\n')
    groups[-1:] = groups[-1].rsplit('.', 1)
    return tuple(groups)

This will be the same output as above except that 'Test2.wma' becomes ('Test2', 'wma'), with similar behavior for 'Test5,7,8.sss' and 'Test5,7,8.sss'.