Expand certain substrings elegantly inside a larger string in python

Question

Hi I want to elegantly expand the substring of the type 4-6 to 4,5,6 in a larger string like

s = "235:2,4,6-9,12,14-19;240:3,5-9,10;245:4,9,10-15,18"

print expand(s)
235:2,4,6,7,8,9,12,14,15,16,17,18,19;240:3,5,6,7,8,9,10;245:4,9,10,11,12,13,14,15,18

Using Python.

Is there some regexp voodoo or similar for this? Thanks a lot!

just use "," as delimiter to split string into array and then iterate through array of elements. If there will be "-" contained extract both numbers and insert expended version of given interval. — Martin V.
– Martin V., Commented Apr 10, 2013 at 5:43
@MartinV.: note that there appear to be two kinds of delimiters. — georg
– georg, Commented Apr 10, 2013 at 6:58

Bakuriu · Accepted Answer · 2013-04-10 08:45:25Z

3

You can do:

>>> import re
>>> def repl(match):
...     start, end = match.groups()
...     return ','.join(str(i) for i in range(int(start), int(end)+1))
... 
>>> re.sub(r'(\d+)-(\d+)', repl, "235:2,4,6-9,12,14-19;240:3,5-9,10;245:4,9,10-15,18")
'235:2,4,6,7,8,9,12,14,15,16,17,18,19;240:3,5,6,7,8,9,10;245:4,9,10,11,12,13,14,15,18'

This uses the fact that the repl argument to re.sub can be a callable that takes as argument the match and returns the replacing string.

The expand(s) function would then be:

import re

def repl(match):
    start, end = match.groups()
    return ','.join(str(i) for i in range(int(start), int(end)+1))

def expand(s):
    return re.sub('(\d+)-(\d+)', repl, s)

edited Apr 10, 2013 at 8:45

answered Apr 10, 2013 at 5:43

Bakuriu

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2 Comments

Blckknght Over a year ago

You might simplify the function a bit if you put parentheses around the d+ parts of the pattern, then used start, end = match.groups().

Bakuriu Over a year ago

Why was this downvoted? I believe it answers exactly the OP's question, so whoever downvoted please give an explanation of you you think this is not only a good solution but completely wrong(as for the FAQ about when to downvote).

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