referrers

[raghu]

Hi All,

The sys.getrefcount () is very useful to get the number of references on
a particular object.

Is there any companion function to get "who" the referrers are ?

for e.g.

global x
global y
global z


x0=24012
y=x0
z=x0

print "ref count ",sys.getrefcou nt(x0)


This prints a ref count of 5.

Basically, I need to know which are the 5 entities who are referring to
x0 ?

Is there any way of doing it ?

Thanks.

Bye,
raghavan V

[Diez B. Roggisch]

Re: referrers

raghu wrote:
[color=blue]
> Hi All,
>
> The sys.getrefcount () is very useful to get the number of references on
> a particular object.
>
> Is there any companion function to get "who" the referrers are ?
>
> for e.g.
>
> global x
> global y
> global z
>
>
> x0=24012
> y=x0
> z=x0
>
> print "ref count ",sys.getrefcou nt(x0)
>
>
> This prints a ref count of 5.
>
> Basically, I need to know which are the 5 entities who are referring to
> x0 ?
>
> Is there any way of doing it ?[/color]

Look into the gc-module.

Diez

[raghu]

Re: referrers

Diez,

I did look into gc, specifically gc.get_referrer s(), but it seemed to
give me something that I cant decipher.

I added the following line.

print "referrers ",gc.get_referr ers(x0)

This is what I got.

referrers [{'__builtins__' : <module '__builtin__' (built-in)>,
'__file__': './tst1.py', 'pdb': <module 'pdb' from
'/home/raghavan/Python-2.4/my_install/lib/python2.4/pdb.pyc'>, 'sys':
<module 'sys' (built-in)>, 'y': 24012, 'gc': <module 'gc' (built-in)>,
'myfuncs': <module 'myfuncs' from '/home/Raghavan/tst/myfuncs.dll'>,
'__name__': '__main__', 'x0': 24012, 'z': 24012, 'os': <module 'os'
from '/home/raghavan/Python-2.4/my_install/lib/python2.4/os.pyc'>,
'__doc__': None, 'types': <module 'types' from
'/home/raghavan/Python-2.4/my_install/lib/python2.4/types.pyc'>},
(None, '/home/Raghavan/tst', 'my pid is ', 24012, 'ref count ',
'referrers ')]

Also the len of this is 2, while I got refcount=5. So I dont know
whether this can be used in the same way.

Thanks.

Bye,
Raghavan V

[Diez B. Roggisch]

Re: referrers

raghu wrote:
[color=blue]
> Diez,
>
> I did look into gc, specifically gc.get_referrer s(), but it seemed to
> give me something that I cant decipher.
>
> I added the following line.
>
> print "referrers ",gc.get_referr ers(x0)
>
> This is what I got.
>
> referrers [{'__builtins__' : <module '__builtin__' (built-in)>,
> '__file__': './tst1.py', 'pdb': <module 'pdb' from
> '/home/raghavan/Python-2.4/my_install/lib/python2.4/pdb.pyc'>, 'sys':
> <module 'sys' (built-in)>, 'y': 24012, 'gc': <module 'gc' (built-in)>,
> 'myfuncs': <module 'myfuncs' from '/home/Raghavan/tst/myfuncs.dll'>,
> '__name__': '__main__', 'x0': 24012, 'z': 24012, 'os': <module 'os'
> from '/home/raghavan/Python-2.4/my_install/lib/python2.4/os.pyc'>,
> '__doc__': None, 'types': <module 'types' from
> '/home/raghavan/Python-2.4/my_install/lib/python2.4/types.pyc'>},
> (None, '/home/Raghavan/tst', 'my pid is ', 24012, 'ref count ',
> 'referrers ')]
>
> Also the len of this is 2, while I got refcount=5. So I dont know
> whether this can be used in the same way.[/color]

The refcount is always precise - as it is a simple integer that happens to
be part of every python object. But the 1:n-relation to its referres is
computed and not necessarily complete, as the docs state very clear.

Additionally, they state that this method is only to be used for
debugging-purposes.

I'm not sure what you are after here - if it is about solving a mem-leak, gc
might help. If it is some application logic, the advice must be clearly to
explicitly model the object graph bi-directional.

Diez