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Get named groups from a regular expression

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  Get named groups from a regular expression Florian Lindner <mailinglists@xgm.de> - 2014-07-01 17:12 +0200
    Re: Get named groups from a regular expression jkn <jkn_gg@nicorp.f9.co.uk> - 2014-07-01 13:49 -0700
    Re: Get named groups from a regular expression Philip Shaw <jnufcvyvuc@tznvy.pbz> - 2014-07-03 23:30 +0000

#73792 — Get named groups from a regular expression

Hello,

Is there a way I can extract the named groups from a regular expression? 
e.g. given "(?P<testgrp>\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

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#73808

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<testgrp>\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

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#73927

On 2014-07-01, Florian Lindner <mailinglists@xgm.de> wrote:
>
> Is there a way I can extract the named groups from a regular
> expression?  e.g. given "(?P<testgrp>\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.

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