[Python-ideas] bool keyword: (was [Python-Dev] bool conversion wart?)

[Greg Ewing]

Ron Adam wrote:
> 
> Greg Ewing wrote:
> 
>> The fact that bool() can be used canonicalise a truth
>> value is secondary
> 
> It seems to me it is the main use, with testing for bool types as the 
> secondary use.

What I meant was that this usage is not reason enough
on its own for bool to be a type. Given that bool is
already a type, it's convenient for its constructor
to also be the canonicalising function. It's secondary
as a reason for making bool a type, not in the sense
of how it's normally used.

> having bool be a 
> subclass of int increases the situations where bool is useful in a nice 
> way.

I still think that most of those uses could be covered
by giving bool an __index__ method.

> Making True and False protected objects along with making bool a keyword 
> may have some performance benefits since in many cases the compiler 
> could then directly return the already constructed True and False object 
> instead of creating new one(s).  [it may already do this under the 
> covers in some cases(?)]

I believe that True and False are treated as singletons,
so this should always happen.

I don't see anywhere enough benefit to be worth making
a bool keyword.

Optimisation of access to True and False is probably
better addressed through a general mechanism for optimising
lookups of globals, although I wouldn't object if they
were treated as reserved identifiers a la None.

Summary of my position on this:

+0   making bool a separate type with __index__ in 3.0
+0   treating True and False like None
-1   bool keyword

--
Greg