[Python-Dev] PEP 362 Third Revision

[R. David Murray]

On Thu, 14 Jun 2012 21:57:34 +0200, Antoine Pitrou <solipsis at pitrou.net> wrote:
> On Thu, 14 Jun 2012 12:46:38 -0700
> Ethan Furman <ethan at stoneleaf.us> wrote:
> > 
> > This is no different from what we have with strings now:
> > 
> > --> 'aA'.islower()
> > False
> > --> 'aA'.isupper()
> > False
> > --> 'a'.islower()
> > True
> > --> 'A'.isupper()
> > True
> > 
> > We know that a string cannot be both all-upper and all-lower at the same 
> > time;
> 
> We know that because it's common wisdom for everyone (although who knows
> what oddities the unicode consortium may come up with in the future).

Indeed, there is at least one letter that is used in both upper case and
lower case, so the consortium could reasonably declare that it should
return True for both isupper and islower :).

I'm not going to claim that there was that much foresight in the creation
of those two methods.  I will, however, note that we aren't perfectly
consistent in the application of our rules.

--David