How to write a regex in Python with named groups to match this?

Question

I have a file which would contain the following lines.

comm=adbd pid=11108 prio=120 success=1 target_cpu=001

I have written the following regex to match.

_sched_wakeup_pattern = re.compile(r"""
comm=(?P<next_comm>.+?)
\spid=(?P<next_pid>\d+)
\sprio=(?P<next_prio>\d+)
\ssuccess=(?P<success>\d)
\starget_cpu=(?P<target_cpu>\d+)
""", re.VERBOSE)

But now I've lines like the following also where the success component isn't there.

comm=rcu_preempt pid=7 prio=120 target_cpu=007

How do I modify my regex here to match both the cases? I tried by putting a * everywhere in that line containing "success", but it throws errors.

Answer 1

The solution using a regex non-capturing group and the regex.findall function:

import regex
...
fh = open('lines.txt', 'r');  // considering 'lines.txt' is your initial file
commlines = fh.read()

_sched_wakeup_pattern = regex.compile(r"""
comm=(?P<next_comm>[\S]+?)
\spid=(?P<next_pid>\d+)
\sprio=(?P<next_prio>\d+)
(?:\ssuccess=)?(?P<success>\d)?
\starget_cpu=(?P<target_cpu>\d+)
""", regex.VERBOSE)

result = regex.findall(_sched_wakeup_pattern, commlines)

template = "{0:15}|{1:10}|{2:9}|{3:7}|{4:10}" # column widths
print(template.format("next_comm", "next_pid", "next_prio", "success", "target_cpu")) # header

for t in result:
    print(template.format(*t))

Beautified output:

next_comm      |next_pid  |next_prio|success|target_cpu
rcu_preempt    |7         |120      |       |007       
kworker/u16:2  |73        |120      |       |006       
kworker/u16:4  |364       |120      |       |005       
adbd           |11108     |120      |1      |001       
kworker/1:1    |16625     |120      |1      |001       
rcu_preempt    |7         |120      |1      |002