re Questions

[Mark Lawrence]

On 26/01/2014 17:25, Chris Angelico wrote:
> 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
>

I suggest a single warning is always given "Regular expressions can be 
fickle.  Have you considered using string methods?".  My apologies to 
regex fans if they're currently choking over their tea, coffee, cocoa, 
beer, scotch, saki, ouzo or whatever :)

-- 
My fellow Pythonistas, ask not what our language can do for you, ask 
what you can do for our language.

Mark Lawrence