[Zope-dev] Pointer or reference object

[Jason Spisak]

Itamar Shtull-Trauring writes:

> Jason Spisak wrote:
> 
> > I had thought that Itamar's code below created an object that was exactly
> > like the object at the URL.  More like a copy.  A duplicate.  It that
> > right?
> 
> No, it doesn't create a duplicate - it actually links twice to the same
> object.
> 
> > what do you mean by reference count?  Something that keeps track of all the
> > references in the ZODB in one place.  An authority?
> 
> Python has a reference count for each object.  When it reached 0 the object
> is deleted.  Consider the following example:
> 
> >>> x = []
> >>> a = x       # a and x both point at the same object
> >>> a.append(3) # so if we change a...
> >>> a
> [3]
> >>> x           # ...x is also changed
> [3]
> >>> del x       # this does not free any memory since a still points at this object
> >>> x
> Traceback (innermost last):
>   File "<stdin>", line 1, in ?
> NameError: x
> >>> a           # a still points at the data
> [3]
> 
> -- 
> Itamar S.T.  itamars@ibm.net


Jason Spisak
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