Context:
When running a regex match in Perl, $1, $2 can be used as references to captured regex references from the match, similarly in Python \g<0>,\g<1> can be used

Perl also has a $ special reference which refers to the captured group with highest numerical value

My question:
Does Python have an equivalent of $ ?

I tried \g< > and tried looking in the documentation which only says:

There’s also a syntax for referring to named groups as defined by the (?P<name>...) syntax. \g<name> will use the substring matched by the group named name, and \g<number> uses the corresponding group number. \g<2> is therefore equivalent to \2, but isn’t ambiguous in a replacement string such as \g<2>0. (\20 would be interpreted as a reference to group 20, not a reference to group 2 followed by the literal character '0'.) The following substitutions are all equivalent, but use all three variations of the replacement string.

CodePudding user response：

>>> import re
>>> s = 'group2'
>>> m = re.search( r'(group1)|(group2)|(group3)', s )
>>> [ g for g in m.groups() if g is not None ]
['group2']

CodePudding user response：

Suppose you have an arbitrary length match (ie, for some reason you don't know how many capture groups.)

You can use re.groups() to get a tuple of all matches and then use relative addressing to get the last.

Example:

>>> s='123456789'
>>> m=re.search(r'(\d)(\d)(\d)', s)
>>> m.groups()
('1', '2', '3')
>>> m.groups()[-1]
'3'

Same as Perl:

% echo '123456' | perl -lnE 'say $  if /(\d)(\d)(\d)/'
3