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+--- Thread: regular expression questions using module re (/thread-21943.html)
regular expression questions using module re - Skaperen - Oct-22-2019
1. i need to match 2 possible forms of a file name. what i did was put one form on each side of a vertical bar ('|'). what i am wondering is how to deal with groups because one form has all 3 groups and the other form has only 2 groups. do i need to have the same number of groups on each side of the vertical bar? or can i use '()' to include a dummy group? or will the .groups() method just return a 3-tuple in one case and a 2-tuple if the other matches?
2. in my expression is a match group for a particular pattern, but if the string has more than one such pattern i want to match the last one and get whatever that pattern is in the string when calling .groups(). how can i be sure of that?
RE: regular expression questions using module re - Gribouillis - Oct-22-2019
For question 1, the match object will always have 5 groups, for example
>>> import re
>>> p = re.compile(r'(f)(o)(o)|(b)(a)r')
>>> match = p.search('This is a foo thing')
>>> match.groups()
('f', 'o', 'o', None, None)
>>> match = p.search('This is a bar thing')
>>> match.groups()
(None, None, None, 'b', 'a')For question 2, I don't understand the question. An example would help.
RE: regular expression questions using module re - Skaperen - Oct-22-2019
if regexp is
'foo(.+)bar' and my string is 'foo123bar...foo789bar' i want to get '789'.
RE: regular expression questions using module re - Gribouillis - Oct-22-2019
You could use
more_itertools.last()>>> import re >>> from more_itertools import last >>> p = re.compile(r'foo(.+?)bar') # <--- note the ? for the non greedy version of + >>> s = 'foo123bar...foo789bar' >>> match = last(p.finditer(s)) >>> match.group(1) '789'
RE: regular expression questions using module re - Skaperen - Oct-22-2019
given the answer to #1 being that it returns 5 groups, and filling in what is matched, then #2 is meaningless.