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

lorin_742 0
Viewed 22488

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',).

python regex
6 Answers

I had this same problem and my solution was to use two regular expressions: the first one to match the whole group I'm interested in and the second one to parse the sub groups. For example in this case, I'd start with this:

VALUE((\s\d+)+)

This should result in three matches: [0] the whole line, [1] the stuff after value [2] the last space+value.

[0] and [2] can be ignored and then [1] can be used with the following:

\s(\d+)

Note: these regexps were not tested, I hope you get the idea though.

The reason why Greg's answer doesn't work for me is because the 2nd part of the parsing is more complicated and not simply some numbers separated by a space.

However, I would honestly go with Greg's solution for this question (it's probably way more efficient).

I'm just writing this answer in case someone is looking for a more sophisticated solution like I needed.

user_3140560

You can use re.match to check first and call re.split to use a regex as separator to split.

>>> s = "VALUE 100 234 568 9233 119"
>>> sep = r"\s+"
>>> reg = re.compile(r"VALUE(%s\d+)+"%(sep)) # OR r"VALUE(\s+\d+)+"
>>> reg_sep = re.compile(sep)
>>> if reg.match(s): # OR re.match(r"VALUE(\s+\d+)+", s)
...     result = reg_sep.split(s)[1:] # OR re.split(r"\s+", s)[1:]
>>> result
['100', '234', '568', '9233', '119']

The separator "\s+" can be more complicated.

user_102094810
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