Re: Get named groups from a regular expression
On 2014-07-01, Florian Lindner wrote: > > Is there a way I can extract the named groups from a regular > expression? e.g. given "(?P\d)" I want to get something > like ["testgrp"]. The match object has an attribute called "groupdict", so you can get the found named groups using match.groupdict.keys. I can't remember what happens to unnamed groups (I prefer to name every group I want), but ISTR that there is a list of capture groups in which the indexes are the capture groups number (i.e. what you'd use to backreference them). > Can I make the match object to return default values for named > groups, even if no match was produced? A lazy solution I've used was to write a default dict, then update it with the groupdict. I doubt that's all that efficient, but the defaults were constant strings and the program was network-bound anyway. -- https://mail.python.org/mailman/listinfo/python-list
Re: Get named groups from a regular expression
On Tue, Jul 1, 2014 at 8:58 AM, Chris Angelico wrote: > On Wed, Jul 2, 2014 at 1:29 AM, Peter Otten <__pete...@web.de> wrote: >> Easy, just write a regular expression to parse regular expressions ;) > > Hmm, is that even possible? AIUI you can't make a regex that correctly > parses nested tokens, and named groups can definitely be nested. Nesting isn't inherently a problem. Since nesting doesn't change the way they parse, you can ignore nesting for the purposes of pulling out named groups. Find each unescaped "(?P<...>". (Making sure they are unescaped is annoying, though.) -- Devin -- https://mail.python.org/mailman/listinfo/python-list
Re: Get named groups from a regular expression
On Tuesday, 1 July 2014 16:12:34 UTC+1, Florian Lindner wrote: > Hello, > > > > Is there a way I can extract the named groups from a regular expression? > > e.g. given "(?P\d)" I want to get something like ["testgrp"]. > > > > OR > > > > Can I make the match object to return default values for named groups, even > > if no match was produced? > > > > Thanks, > > Florian If you can, my approach would to have a class which you use both to create the regex (using group names), and return the names of the groups in the regex you have created. As I say, this might not be possible in your case though. Jon N -- https://mail.python.org/mailman/listinfo/python-list
Re: Get named groups from a regular expression
Chris Angelico wrote: > On Wed, Jul 2, 2014 at 1:29 AM, Peter Otten <__pete...@web.de> wrote: >> Easy, just write a regular expression to parse regular expressions ;) > > Hmm, is that even possible? AIUI you can't make a regex that correctly > parses nested tokens, and named groups can definitely be nested. Hmm, it was a joke. For a limited number of nestings you should be able to cook something up; I think Python allows up to 100 groups, so there is an upper limit of nesting levels. You might need a regex implementation that allows more than 100 groups to parse your regex-parsing regex though... -- https://mail.python.org/mailman/listinfo/python-list
Re: Get named groups from a regular expression
On 2014-07-01 16:12, Florian Lindner wrote:
Hello,
Is there a way I can extract the named groups from a regular expression?
e.g. given "(?P\d)" I want to get something like ["testgrp"].
OR
Can I make the match object to return default values for named groups, even
if no match was produced?
import re
r = re.compile(r"(?P\d)")
r.groupindex
{'testgrp': 1}
i.e. there's a named group called 'testgrp' whose group number is 1.
--
https://mail.python.org/mailman/listinfo/python-list
Re: Get named groups from a regular expression
On Wed, Jul 2, 2014 at 1:29 AM, Peter Otten <__pete...@web.de> wrote: > Easy, just write a regular expression to parse regular expressions ;) Hmm, is that even possible? AIUI you can't make a regex that correctly parses nested tokens, and named groups can definitely be nested. ChrisA -- https://mail.python.org/mailman/listinfo/python-list
Re: Get named groups from a regular expression
Florian Lindner wrote: > Is there a way I can extract the named groups from a regular expression? > e.g. given "(?P\d)" I want to get something like ["testgrp"]. Easy, just write a regular expression to parse regular expressions ;) (Sorry, I can't contribute something constructive, my first idea, re.DEBUG doesn't help) > OR > > Can I make the match object to return default values for named groups, > even if no match was produced? -- https://mail.python.org/mailman/listinfo/python-list
