python - Interpret regular expression -

this question has answer here:

• what differences between lazy, greedy , possessive quantifiers? 1 answer

i'm trying parse output looks below.

1  192.168.1.1         0.706 ms  0.654 ms  0.697 ms  2  10.10.10.10         4.215 ms  4.199 ms  4.175 ms 3  123.123.123.123     4.000 ms * * 

i have regular expression works, follows.

this regex works:

re.compile(r'^\s*(\d+)\s+?([\s\s]+?(?=^\s*\d+\s+))', re.m) 

this capture each line properly.

('1', ' 192.168.7.1         0.706 ms  0.654 ms  0.697 ms\n') ('2', ' 10.10.10.10         4.215 ms  4.199 ms  4.175 ms\n') ('3', ' 123.123.123.123     4.000 ms  * *\n') 

my question bold ? in front of (?=^\s*\d+\s+)

i.e. changing regular expression follows.

this regex not work. difference ? mark removed.

re.compile(r'^\s*(\d+)\s+?([\s\s]+(?=^\s*\d+\s+))', re.m) 

i have tried , not work. not parse each line separately.

could me interpret regular expression?

according re docs:

*?, +?, ??

the '\*', '+', , '?' qualifiers greedy; match text possible. behaviour isn’t desired; if re <.*> matched against <a> b <c>, match entire string, , not <a>. adding ? after qualifier makes perform match in non-greedy or minimal fashion; few characters possible matched. using re <.*?> match <a>.

so in case, [\s\s]+? match space or non-space character minimally, whereas [\s\s]+ greedily match many characters can.