On Sat, Aug 29, 2009 at 07:03:23PM +0000, Steven D'Aprano wrote: > On Sat, 29 Aug 2009 11:11:43 -0700, zaur wrote: > > > I thought that int as object will stay the same object after += but with > > another integer value. My intuition said me that int object which > > represent integer value should behave this way. > > If it did, then you would have this behaviour:
No, you wouldn't; the behavior you described is completely different from, and incompatible with, what zaur wrote. He's saying that instead of thinking the integer value of 3 itself being the object, he expected Python's object model would behave as though the entity m is the object, and that object exists to contain an integer value. In that case, m is always m, but it has whatever integer value it is told to hold at any point in time. The self-referential addition would access the value of m, add the operand, and store the result back in the same object as the object's value. This is not the way Python works, but he's saying this is the intuitive behavior. I happen to agree, and argued at length with you and others about that very thing months ago, when some other third party posted with that exact same confusion. By contrast, your description maintains the concept of numerical value as object that Python uses, and completely misses the point. I did find the description you gave to be highly enlightening though... It highlighted perfectly, I think, exactly why it is that Python's behavior regarding numerical values as objects is *not* intuitive. Of course, intuition is highly subjective. I believe it boils down to this: People expect that objects they create are mutable. At least, unless they specify otherwise. It is so in some other programming languages which people may be likely to be familiar with (if they are not taking their first forray into the world of computing by learning Python), and even "real world" objects are essentially always mutable. If you have a 2002 Buick LeSabre, it has a number of attributes, including its length, which might be 8.5 feet, for instance. However, this is not fixed: by adding modified body parts, or as an extreme example by sawing off the trunk of the car, the length and indeed the object itself has been changed. However, despite having been modified, it is at least in some sense still the same object: it is still a 2002 Buick LeSabre, and it still has the same *identity* (the same VIN number). It's the same object, but its value(s) changed. [Not that it matters, but I do not own such a car. :)] Numbers are fundamentally different from objects. The number 3 is a symbol of the idea of the existence of three countable objects. It can not be changed (though it can be renamed, if you so choose -- just don't expect most people to know what you're talking about). It is unintuitive that 3 is an object; it is rather what we use to describe objects -- the value of the object. It is an abstract concept, and as such it is not an object at all. You cannot hear 3, taste 3, nor smell 3. You can neither see nor touch 3, though you can certainly see 3 *objects* if they are present, and you can certainly see the symbol '3' that we use to represent that idea... but you can not see three itself, because there is no such object. The only way to see three is to envision 3 of some object. The number 3 does not have a value; it IS a value (it is the symbolic representation of the value of three). To say that 3 is an object that has a value is a bit like saying the length of a car is an object that itself has a length. It just doesn't compute. THAT is why Python's behavior with regard to numerical objects is not intuitive, and frankly bizzare to me, and I dare say to others who find it so. Yes, that's right. BIZZARE. Of course, none of this is real. In the end, it's all just a bunch of wires that either have current or don't. It's only how *WE* organize and think about that current that gives it any meaning. So you're free to think about it any way you like. -- Derek D. Martin http://www.pizzashack.org/ GPG Key ID: 0x81CFE75D
pgpyymVqHadto.pgp
Description: PGP signature
-- http://mail.python.org/mailman/listinfo/python-list
