[Python-Dev] For review: PEP 285: Adding a bool type

[Guido van Rossum]

> >             def __repr__(self):
> >                 if self:
> >                     return "True"
> >                 else:
> >                     return "False"
> > 
> >             __str__ = __repr__
> 
> I don't like this: it will break too much code since there
> are already two singletons Py_True and Py_False available
> in Python and these return 1 / 0 resp.

But this is the whole point of introducing a new type rather than
simply defining True as 1 and False as 0!

> >         False = bool(0, _create=1)
> >         True = bool(1, _create=1)
> 
> Please adjust Py_True and Py_False (at C level) to be 
> identical to these constants.

Yes, that was the intention.

> > Issues
> > 
> >     Because the repr() or str() of a bool value is different from an
> >     int value, some code (e.g. doctest-based unit tests) may fail.
> >     How much of a backwards compatibility problem this will be, I
> >     don't know.  If we find this is a real problem, we could add a
> >     command-line option to make False and True aliases for 0 and 1 and
> >     bool an alias for int.
> 
> Please, no ! 

Agreed -- I just mentioned it as a possibility if we find too much
problems due to the new repr() and str().

> Ideal would be to make bool a subtype of int and True and
> False two singletons created from 1 and 0 having the bool
> type: that's simple and backwards compatible.

That's what I am proposing.

> One idea for a possible addition:
> 
> Add boolean support to the array module so that it becomes
> possible to create arrays of bits.

That's an entirely separate issue, and would require major hackery to
the array module (if you want the bits to be tightly packed, which I
assume you do).  Let's not mix it up with this.

--Guido van Rossum (home page: http://www.python.org/~guido/)