[Python-Dev] Re: PEP 285: Adding a bool type (original) (raw)

Christian Tanzer tanzer@swing.co.at
Mon, 01 Apr 2002 09:14:59 +0200

Tim Peters <tim.one@comcast.net> wrote:

[Christian Tanzer] > ... > If str and repr were to behave differently from each other, I'd expec= t > repr(True) to return "1" and str(True) to return "True". Interchangin= g > that seems strange.

We try to ensure that eval(repr(x)) reproduce x whenever reasonably possible. That best way to do that here is for repr(True) to return 'True'.

I understood the motivation for repr(bool(1)) =3D=3D "True".

What I wanted to say is that having repr return a readable result and str return a result looking like an internal representation runs counter to the usual conventions used for repr and str.

> OTOH, I'm worried about backwards compatibility.

That's the only reason for str(True) to return '1'.

In this case, I'd value consistency between repr/str higher than backwards compatibility.

How about str(True) return '1' but str(False) return 'False'? That's what a committee would compromise on .

Any self respecting committee would try harder and probably come up with a really symmetric compromise:

value    str      repr
True     '1'      'True'
False    'False'  '0'

<1.4. wink>

> How will bool influence 'nonzero'? Currently, Python insists that=

> 'nonzero should return an int'. Will this be changed to 'should > return a bool'?

I hope so. > As that would break existing code, I hope not. No, "should" !=3D "must".

Fine display of sophisticated hair splitting, but:

>>> class Foo:
...   def __nonzero__(self): return None
...
>>> f =3D Foo ()
>>> not f
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
TypeError: __nonzero__ should return an int
>>>

I don't care about should vs. must as long as the new and improved Python won't spit an exception at nonzero code returning an int instead of a bool.

Guido won't call code that returns an int here broken, although he might call it deprecated, and leave you wondering when the hammer will drop .

Nice tease. But Guido's hammer with regard to future strictification of bool is exactly what makes me uneasy.

-- =

Christian Tanzer tanzer@swing.co.= at Glasauergasse 32 Tel: +43 1 876 62 = 36 A-1130 Vienna, Austria Fax: +43 1 877 66 = 92