[Tutor] regex grouping/capturing

[Albert-Jan Roskam]

Hello,
 
I have a string of the form "required optional3 optional2 optional1 optional3" ('optional' may be any kind of string, so it's not simply 'optional\d+'.
I would like to use a regex so I can distinguish groups. Desired outcome: ('required', 'optional3', 'optional2', 'optional1', 'optional3'). Below is 
a fragment of the many things I have tried.
 
>>> import re
>>> regex = r"(required) (optional1)* (optional2)* (optional3)*"
>>> #regex = r"(required) (?:(optional1)*|(optional2)*|(optional3)*)*"
>>> #regex = r"(required) (optional1|optional2|optional3)*"
>>> s = "required optional3 optional2 optional1 optional3"
>>> re.search(regex, s).groups()
Traceback (most recent call last):
  File "<pyshell#8>", line 1, in <module>
    re.search(regex, s).groups()
AttributeError: 'NoneType' object has no attribute 'groups'
>>> s2 = "required optional1 optional2 optional3"
>>> re.search(regex, s2).groups()
('required', 'optional1', 'optional2', 'optional3') # it only 'works' if the optional words are in the same order as in the regex, and not specified multiple times.

How can I make this work? 

Thank you in advance!

Regards,
Albert-Jan


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