On Tue, 10 Jul 2007 16:56:36 -0700, Paul Rubin wrote:
> We had a huge discussion of this stuff when bools were introduced in
> Python 2.3 or thereabouts. The current system is about the best way
> that doesn't break everything in sight.
But Python 3 is allowed to break backwards compatibility, so that's no
longer a reason for keeping the current behaviour.
> The weirdness is basically a
> consequence of bools being an afterthought in Python. Python has a long
> tradition of implicitly casting other values to bool, e.g. strings,
> lists, sets etc. are all false if empty, etc.
No, that's not true. How could Python cast objects to bool before bool
existed?
What Python has is much more powerful: the concept of Something versus
Nothing. "x" and 4 and [23, "foo"] are all Something. "" and 0 and [] and
None are all Nothing. No cast, whether implicit or explicit, is needed.
What Python does is call the object's __nonzero__ method, if it has one,
otherwise it checks to see if the object has a non-zero length (if it has
a length), and otherwise the object is considered true.
>From a purely functional perspective, bools are unnecessary in Python. I
think of True and False as syntactic sugar. But they shouldn't be
syntactic sugar for 1 and 0 any more than they should be syntactic sugar
for {"x": "foo"} and {}.
--
Steven.
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