[Python-ideas] Make undefined escape sequences have SyntaxWarnings

[Antoine Pitrou]

On Wed, 10 Oct 2012 16:08:22 -0400
Mike Graham <mikegraham at gmail.com> wrote:
> On Wed, Oct 10, 2012 at 3:46 PM, Antoine Pitrou <solipsis-xNDA5Wrcr86sTnJN9+BGXg at public.gmane.org> wrote:
> > On Wed, 10 Oct 2012 15:36:08 -0400
> > Mike Graham <mikegraham at gmail.com> wrote:
> >> The literal"\c" should be an error but in practice means "\\c". It's
> >> probably too late to make this invalid syntax as it out to be, but I
> >> wonder if a warning isn't in order, especially with the theoretical
> >> potential of adding new string escapes in the future.
> >
> > -1. This will make life more difficult with regular expressions (and
> > produce lots of spurious warnings in existing code).
> >
> > Regards
> >
> > Antoine.
> 
> Regular expressions are difficult if you're remembering which escape
> sequences exist and are easy if you're using raw string literals.

That's a misconception, since as the re docs mention:

“Most of the standard escapes supported by Python string literals are
also accepted by the regular expression parser: [snip]”

http://docs.python.org/dev/library/re.html

In other words, whether you put "\t" or "\\t" in a regexp doesn't
matter: it means the same to the regexp engine.

Regards

Antoine.


-- 
Software development and contracting: http://pro.pitrou.net