By value or by reference?

[Alex Martelli]

Gustavo Niemeyer <niemeyer at conectiva.com> wrote:
   ...
> It really depends on what you claim to be passed by value. In Python,
> objects are passed by reference, but references are passed by value. So
> one may say that z is being passed by value, since what is passed is a
> copy of the reference. With that in mind, one may correctly say that
> Python always do pass-by-value, and correctly say that it always do
> pass-by-reference.

That's my point, even though it's argued the other way 'round, that
neither is correct, given the usual connotations of these terms.


> Here is an article presenting the issue in more detail (much more :-):
> 
> http://www-106.ibm.com/developerworks/java/library/j-passbyval/
> 
> > The terminology problem may be due to the fact that, in python, the
> > value of a name is a reference to an object.  So, you always pass the
> > value (no implicity copying), and that value is always a reference.
> [...]
> 
> That's it.

Right.  And in common use, pass-by-value and -by-reference are thought
to imply something else.  I wonder how Java deals with it, since (except
for some primitive types like int) it's just the same mechanism as
Python's; being widely used and academically acceptable it must have
found a satisfactory way to explain this, one would hope.


Alex