Use of compile flags in regular expressions.

MRAB python at mrabarnett.plus.com
Thu Jul 19 17:15:33 CEST 2012


On 19/07/2012 15:22, Steven W. Orr wrote:
> I have a problem that I'm solving using a regex. (Yeah, I know, now I have two
> problems...) ;-)>
>
> Anyways, the regex is about a couple of pages long and it works just peachy.
> There's just one thing I'd like to do to make it more elegant.
>
> I need to compile the regex with MULTILINE and DOTALL. But there are a few
> sections where I wish it was *not* compiled with DOTALL. For those cases, I
> use (something like)
>
> [^\n]*
>
> instead of
>
> .*
>
> I see that I can use the (?MS) construct but I also see that it applies
> globally and not to the subgroup that I'm using it in.
>
> * Is there a way to make it apply locally to a subgroup?

It with the re module.

> * If not, is there another way?

The DOTALL . could be replaced with, say, [\d\D].

> * Also, is this an incredible stroke of genius that I came up with this idea
> of applying flags to a subgroup, or have others thought of this too and found
> out that it's not really a good idea?
>
Many other regex implementations do support scoped flags, including the
one here:

http://pypi.python.org/pypi/regex

which is designed to be backwards-compatible with the re module.



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