counting references to an instance

[Brian]

Hello;

Is it possible to get an object to return the number of references there
are to itself?

Ex:

class test(object):
pass

a = test()
b = a

# Should print "2", if I knew the name of the method.
print a.refCount()

Many thanks,

Brian.

[Thomas Heller]

Re: counting references to an instance

Brian <balex@sympatic o.ca> writes:
[color=blue]
> Hello;
>
> Is it possible to get an object to return the number of references there
> are to itself?
>
> Ex:
>
> class test(object):
> pass
>
> a = test()
> b = a
>
> # Should print "2", if I knew the name of the method.
> print a.refCount()
>[/color]

In Python debug builds, there's the sys.getrefcount () function.

Thomas

[Aahz]

Re: counting references to an instance

In article <pan.2004.02.04 .18.55.02.38509 2.6672@sympatic o.ca>,
Brian <balex@sympatic o.ca> wrote:[color=blue]
>
>Is it possible to get an object to return the number of references there
>are to itself?
>
>Ex:
>
>class test(object):
> pass
>
>a = test()
>b = a
>
># Should print "2", if I knew the name of the method.
>print a.refCount()[/color]

sys.getrefcount (a) will do the trick -- but it will print 3. Can you
figure out why?
--
Aahz (aahz@pythoncra ft.com) <*> http://www.pythoncraft.com/

"The joy of coding Python should be in seeing short, concise, readable
classes that express a lot of action in a small amount of clear code --
not in reams of trivial code that bores the reader to death." --GvR

[Brian]

Re: counting references to an instance

On Wed, 04 Feb 2004 14:57:59 -0500, Aahz wrote:
[color=blue]
> In article <pan.2004.02.04 .18.55.02.38509 2.6672@sympatic o.ca>, Brian
> <balex@sympatic o.ca> wrote:[color=green]
>>
>>Is it possible to get an object to return the number of references there
>>are to itself?
>>
>>Ex:
>>
>>class test(object):
>> pass
>>
>>a = test()
>>b = a
>>
>># Should print "2", if I knew the name of the method. print a.refCount()[/color]
>
> sys.getrefcount (a) will do the trick -- but it will print 3. Can you
> figure out why?[/color]

Does the instance of test contain a reference to itself?

Brian.

[Aahz]

Re: counting references to an instance

In article <pan.2004.02.04 .21.00.59.32256 4.7241@sympatic o.ca>,
Brian <balex@sympatic o.ca> wrote:[color=blue]
>On Wed, 04 Feb 2004 14:57:59 -0500, Aahz wrote:[color=green]
>> In article <pan.2004.02.04 .18.55.02.38509 2.6672@sympatic o.ca>, Brian
>> <balex@sympatic o.ca> wrote:[color=darkred]
>>>
>>>Is it possible to get an object to return the number of references there
>>>are to itself?
>>>
>>>Ex:
>>>
>>>class test(object):
>>> pass
>>>
>>>a = test()
>>>b = a
>>>
>>># Should print "2", if I knew the name of the method. print a.refCount()[/color]
>>
>> sys.getrefcount (a) will do the trick -- but it will print 3. Can you
>> figure out why?[/color]
>
>Does the instance of test contain a reference to itself?[/color]

Nope. Robert Brewer's response explained it.
--
Aahz (aahz@pythoncra ft.com) <*> http://www.pythoncraft.com/

"The joy of coding Python should be in seeing short, concise, readable
classes that express a lot of action in a small amount of clear code --
not in reams of trivial code that bores the reader to death." --GvR

[Michael Hudson]

Re: counting references to an instance

Thomas Heller <theller@python .net> writes:
[color=blue]
> Brian <balex@sympatic o.ca> writes:
>[color=green]
> > Hello;
> >
> > Is it possible to get an object to return the number of references there
> > are to itself?
> >
> > Ex:
> >
> > class test(object):
> > pass
> >
> > a = test()
> > b = a
> >
> > # Should print "2", if I knew the name of the method.
> > print a.refCount()
> >[/color]
>
> In Python debug builds, there's the sys.getrefcount () function.[/color]

In *all* builds, there's sys.getrefcount (). Are you thinking of
sys.gettotalref count()?

--
ARTHUR: Yes. It was on display in the bottom of a locked filing
cabinet stuck in a disused lavatory with a sign on the door
saying "Beware of the Leopard".
-- The Hitch-Hikers Guide to the Galaxy, Episode 1

[Thomas Heller]

Re: counting references to an instance

Michael Hudson <mwh@python.net > writes:
[color=blue]
> Thomas Heller <theller@python .net> writes:[color=green]
>>
>> In Python debug builds, there's the sys.getrefcount () function.[/color]
>
> In *all* builds, there's sys.getrefcount (). Are you thinking of
> sys.gettotalref count()?[/color]

Yes, probably. Thanks for the correction.

Thomas