Chris Angelico wrote:
On Sun, Sep 24, 2017 at 8:18 AM, Bill <bill_nos...@whoknows.net> wrote:
Stephan Houben wrote:
Op 2017-09-23, Rick Johnson schreef <rantingrickjohn...@gmail.com>:
These pissing contests over how values are passed in Python
are totally irrelevant. What does it matter? Nothing will be
gained or lost by arguing over which is true, or not. Unless
the distinction is preventing you from doing something that
you'd like to do, or unless you want to argue that one
"value passing method" would bring X, Y or Z benefits over
the other, what does it matter?
Amen.
All one has to do, I think, is consider (1) that passing objects by "making
copies" of them, would be prohibitively expensive and consider that
something else has to happen as an alternative, and (2) understand that in
Python, objects don't have names, they have references (which have names).
The rest could be "implementation dependent" (no?) To be amusing, how did
the chicken pass an egg to the_other_side_of_the_road(e)? Could the egg get
crushed (stay tuned)?
Actually they don't "have" references in any real sense of possession.
I agree (I was a bit hasty in my choice of words); but if they didn't
"have" these references, it would be difficult, though not impossible,
to refer to them. Also keep in mind that the garbage collector keeps
track, generally, of how many there are for each object! So from the
gc's point of view, objects (definitely) "have" references. Next,
what will Egg.__del__() do? : )
An object "has" things like its type, its attributes, etc etc; if you
have a reference to an object, you can query it for its type. But you
can't ask an object if there's a reference to it over here or there.
(Yes, I know that sys.getrefcount exists in CPython, but this isn't
part of the language's definition. Also, even that is just a counter -
you can't find specific references.) An object may have a reference to
other objects (eg a list's contents), but it's a one-way thing -
there's no way to find all the references to this object.
So more accurate would be to say that objects don't have names, but
names refer to objects. When you assign to a simple name, you cause
that name to refer to the object you gave it.
ChrisA
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