John Yeung a écrit :
On Jun 13, 2:29 am, Steven D'Aprano
<st...@removethis.cybersource.com.au> wrote:
Paul LaFollette wrote:
3) (this is purely philosophical but I am curious)
Would it not be more intuitive if
isinstance(None, <anything at all>) returned true?
Good grief no!!!
None is an object. It has a type, NoneType. It's *not* a
string, or a float, or an int, or a list, so why would
you want isinstance() to *lie* and say that it is?
Because you might want None to behave as though it were nothing at
all.
Paul LaFollette is probably thinking along the lines of formal logic
or set theory. It's a little bit confused because programming isn't
quite the same as math, and so it's a common question when designing
and implementing programming languages how far to take certain
abstractions. In some languages, nil, null, or none will try to
behave as mathematically close to "nothing" (complete absence of
anything) as possible, even though in reality they have to have some
concrete implementation, such as perhaps being a singleton object.
But mathematically speaking, it's intuitive that "nothing" would match
any type.
IOW, what's the OP is after is not the None type, but some yet
unexisting "Anything" type !-)
--
http://mail.python.org/mailman/listinfo/python-list
