re Questions

[Chris Angelico]

On Mon, Jan 27, 2014 at 4:15 AM, Roy Smith <roy at panix.com> wrote:
> In article <mailman.5996.1390756093.18130.python-list at python.org>,
>  Chris Angelico <rosuav at gmail.com> wrote:
>
>> The set [A-z] is equivalent to
>> [ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz]
>
> I'm inclined to suggest the regex compiler should issue a warning for
> this.
>
> I've never seen a character range other than A-Z, a-z, or 0-9.  Well, I
> suppose A-F or a-f if you're trying to match hex digits (and some
> variations on that for octal).  But, I can't imagine any example where
> somebody wrote A-z and it wasn't an error.

I've used a variety of character ranges, certainly more than the 4-5
you listed, but I agree that A-z is extremely likely to be an error.
However, I've sometimes used a regex (bytes mode) to find, say, all
the ASCII printable characters - [ -~] - and I wouldn't want that
precluded. It's a bit tricky trying to figure out which are likely to
be errors and which are not, so I'd be inclined to keep things as they
are. No warnings.

ChrisA