[Python-Dev] PEP 362 Third Revision

[Antoine Pitrou]

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).
Whether a given function argument may be of several kinds at the same
time is much less obvious to most people.

Regards

Antoine.