As that string has extra double quotes,can do tricks and match between quotes.
For testing regex look at regex101.
There also a Regular Expression HOWTO and the regular doc.
For testing regex look at regex101.
There also a Regular Expression HOWTO and the regular doc.
>>> import re
>>>
>>> line2 = '"555 102 4 21", "39 555 6", "555 102"'
>>> r = re.findall(r'"(.*?)"', line2)
>>> r
['555 102 4 21', '39 555 6', '555 102']
>>> r[0]
'555 102 4 21'
>>> [int(i) for i in r[0].split()]
[555, 102, 4, 21]
>>> # Or think of why this work,hint new PEP
>>> g = r[0].replace(' ', '_')
>>> g
'555_102_4_21'
>>> int(g)
555102421
# No error using underscore in integer
>>> 100_000_000_123
100000000123