[Tutor] regex newbie question

[Steve Willoughby]

Dick Moores wrote:
> At 04:32 PM 5/8/2008, Steve Willoughby wrote:
>> On Thu, May 8, 2008 14:40, Dick Moores wrote:
>> > At 01:30 PM 5/8/2008, Steve Willoughby wrote:
>> >>On Thu, May 8, 2008 12:40, Dick Moores wrote:
>> >> > But here's a chance to ask: What regex would match 2-digit strings
>> >> > and 4-digit strings only?
>> >>
>> >>^\d\d(\d\d)?$
>> >
>> > Ah. And so ^\d\d(\d\d)?(\d\d)?$ matches all and only 2-, 4-, and
>> > 6-digit strings.  Which makes me wonder if there's a regex for ALL
>> > and only strings of digits only, with an even number of digits.
>>
>> That would be r'^\d\d(\d\d)*$'
> 
> OK!
> 
> I bought RegexBuddy (<http://www.regexbuddy.com/>) today, which is a big 
> help. However, it has a comment about your regex--I think it's saying 
> you are wrong--tho it sure does the job for me with

No, the comment was warning you that something wouldn't work, but it's
not what you were trying to do anyway.  Sort of "If you were intending
for this side effect to work in addition to matching even numbers of
digits..."  But that doesn't apply to your stated problem.


> 
> VALID
> 12
> 1234
> 123456
> 12345678
> 1234567890
> 1234567890112345678901
> INVALID
> 1
> 123
> 12345
> 1234567
> 123456789
> 12345678901
> 123456789011234567890
> 
> in matching all the valids and none of the invalids.
> 
> What say you? See 
> <http://www.rcblue.com/Regex/all_even_number_of_digits.htm>
> 
> Thanks very much,
> 
> Dick
> 
> 
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