Python regular expression: extract multiple matching groups

Question

I want to match the last N digits in a line of text. I know I can use re.findall to simply extract all digits and then count back N but I am interested to know if I can extract N groups using re.match. I have this:

line = 'humpty dumpty 25 1, 2, 3, 4, 5, 6'
N = 6
p = re.compile('^(.+)(\D+\d+){{{0}}}$'.format(N))
m = re.match(p, line)

I get a match OK. However I want to access each of 1, 2, 3, 4, 5, 6 but all I get is:

>>> m = re.match(p, line)
>>> m.group(0)
'humpty dumpty 25 1, 2, 3, 4, 5, 6'
>>> m.group(1)
'humpty dumpty 25'
>>> m.group(2)
', 6'
>>> m.group(3)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
IndexError: no such group

I want to see a group for each digit. Can re.match be used in the way I am attempting?

Thanks.

You cannot use it that way in Python. You need a separate method that will do that. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Nov 2, 2015 at 23:10

R Nar · Accepted Answer · 2015-11-02 23:12:24Z

5

your problem is that if you do a repeat of groups, it will only capture the last instance of that group. you have to set a different group for each capture you want. this line below works:

p = re.compile('^(.+)' + '(\D+\d+)'*N + '$')

EXAMPLE:

>>> m = re.match(p, line)
>>> m.groups()
('humpty dumpty 25', ' 1', ', 2', ', 3', ', 4', ', 5', ', 6')

answered Nov 2, 2015 at 23:12

R Nar

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