How do I regex match with grouping with unknown number of groups

Question

I want to do a regex match (in Python) on the output log of a program. The log contains some lines that look like this:

... 
VALUE 100 234 568 9233 119
... 
VALUE 101 124 9223 4329 1559
...

I would like to capture the list of numbers that occurs after the first incidence of the line that starts with VALUE. i.e., I want it to return ('100','234','568','9233','119'). The problem is that I do not know in advance how many numbers there will be.

I tried to use this as a regex:

VALUE (?:(\d+)\s)+

This matches the line, but it only captures the last value, so I just get ('119',).

Answer 1

What you're looking for is a parser, instead of a regular expression match. In your case, I would consider using a very simple parser, split():

s = "VALUE 100 234 568 9233 119"
a = s.split()
if a[0] == "VALUE":
    print [int(x) for x in a[1:]]

You can use a regular expression to see whether your input line matches your expected format (using the regex in your question), then you can run the above code without having to check for "VALUE" and knowing that the int(x) conversion will always succeed since you've already confirmed that the following character groups are all digits.

Answer 2

You could just run you're main match regex then run a secondary regex on those matches to get the numbers:

matches = Regex.Match(log)

foreach (Match match in matches)
{
    submatches = Regex2.Match(match)
}

This is of course also if you don't want to write a full parser.

Answer 3

>>> import re
>>> reg = re.compile('\d+')
>>> reg.findall('VALUE 100 234 568 9233 119')
['100', '234', '568', '9223', '119']

That doesn't validate that the keyword 'VALUE' appears at the beginning of the string, and it doesn't validate that there is exactly one space between items, but if you can do that as a separate step (or if you don't need to do that at all), then it will find all digit sequences in any string.