Get all the instances of one class

[Terry]

Hi,

Is there a simple way to get all the instances of one class? I mean
without any additional change to the class.

br, Terry

[Ben Finney]

Terry <te**********@gmail.comwrites:

Is there a simple way to get all the instances of one class?

Define "all". All the instances in the current scope?

Perhaps more pertinent: What problem are you trying to address?

--
\ “We demand rigidly defined areas of doubt and uncertainty!� |
`\ —Vroomfondel, _The Hitch-Hiker's Guide To The Galaxy_, |
_o__) Douglas Adams |
Ben Finney

[Gabriel Genellina]

En Fri, 16 May 2008 20:44:00 -0300, Terry <te**********@gmail.com>
escribió:

Is there a simple way to get all the instances of one class? I mean
without any additional change to the class.

Try with gc.get_referrers()

pyimport gc
pyclass A(object): pass
....
pya,b,c = A(),A(),A()
pyA
<class __main__.A at 0x00A3F4E0>
pyfor item in gc.get_referrers(A): print type(item)
....
<type 'getset_descriptor'>
<type 'getset_descriptor'>
<type 'tuple'>
<class '__main__.A'>
<class '__main__.A'>
<class '__main__.A'>
<type 'dict'>
<type 'dict'>

We need to filter that list, keeping only A's instances:

py[item for item in gc.get_referrers(A) if isinstance(item,A)]
[<__main__.A object at 0x00A40DC8>, <__main__.A object at 0x00A40DF0>,
<__main__.A object at 0x00A40E18>]

--
Gabriel Genellina

[Terry]

On May 17, 8:04 am, "Gabriel Genellina" <[e-mail]>
wrote:

En Fri, 16 May 2008 20:44:00 -0300, Terry <[e-mail]>
escribió:

Is there a simple way to get all the instances of one class? I mean
without any additional change to the class.

Try with gc.get_referrers()

pyimport gc
pyclass A(object): pass
...
pya,b,c = A(),A(),A()
pyA
<class __main__.A at 0x00A3F4E0>
pyfor item in gc.get_referrers(A): print type(item)
...
<type 'getset_descriptor'>
<type 'getset_descriptor'>
<type 'tuple'>
<class '__main__.A'>
<class '__main__.A'>
<class '__main__.A'>
<type 'dict'>
<type 'dict'>

We need to filter that list, keeping only A's instances:

py[item for item in gc.get_referrers(A) if isinstance(item,A)]
[<__main__.A object at 0x00A40DC8>, <__main__.A object at 0x00A40DF0>,
<__main__.A object at 0x00A40E18>]

--
Gabriel Genellina

Thanks! This is what I'm looking for.

[Terry]

On May 17, 8:04 am, "Gabriel Genellina" <[e-mail]>
wrote:

En Fri, 16 May 2008 20:44:00 -0300, Terry <[e-mail]>
escribió:

Is there a simple way to get all the instances of one class? I mean
without any additional change to the class.

Try with gc.get_referrers()

pyimport gc
pyclass A(object): pass
...
pya,b,c = A(),A(),A()
pyA
<class __main__.A at 0x00A3F4E0>
pyfor item in gc.get_referrers(A): print type(item)
...
<type 'getset_descriptor'>
<type 'getset_descriptor'>
<type 'tuple'>
<class '__main__.A'>
<class '__main__.A'>
<class '__main__.A'>
<type 'dict'>
<type 'dict'>

We need to filter that list, keeping only A's instances:

py[item for item in gc.get_referrers(A) if isinstance(item,A)]
[<__main__.A object at 0x00A40DC8>, <__main__.A object at 0x00A40DF0>,
<__main__.A object at 0x00A40E18>]

--
Gabriel Genellina

But I saw in the help that we should "Avoid using get_referrers() for
any purpose other than debugging. "

[Diez B. Roggisch]

Terry schrieb:

On May 17, 8:04 am, "Gabriel Genellina" <[e-mail]>
wrote:

>En Fri, 16 May 2008 20:44:00 -0300, Terry <[e-mail]>
escribió:

>>Is there a simple way to get all the instances of one class? I mean
without any additional change to the class.

Try with gc.get_referrers()

pyimport gc
pyclass A(object): pass
...
pya,b,c = A(),A(),A()
pyA
<class __main__.A at 0x00A3F4E0>
pyfor item in gc.get_referrers(A): print type(item)
...
<type 'getset_descriptor'>
<type 'getset_descriptor'>
<type 'tuple'>
<class '__main__.A'>
<class '__main__.A'>
<class '__main__.A'>
<type 'dict'>
<type 'dict'>

We need to filter that list, keeping only A's instances:

py[item for item in gc.get_referrers(A) if isinstance(item,A)]
[<__main__.A object at 0x00A40DC8>, <__main__.A object at 0x00A40DF0>,
<__main__.A object at 0x00A40E18>]

--
Gabriel Genellina

But I saw in the help that we should "Avoid using get_referrers() for
any purpose other than debugging. "

Yes, because using it do is very resource-consuming and shouldn't be
done. Why don't you tell us what you are after here & then we might come
up with a better solution?

Diez

[Gabriel Genellina]

En Sun, 18 May 2008 12:32:28 -0300, Terry <te**********@gmail.comescribió:

On May 17, 8:04 am, "Gabriel Genellina" <[e-mail]>
wrote:

>En Fri, 16 May 2008 20:44:00 -0300, Terry <[e-mail]>
escribió:

Is there a simple way to get all the instances of one class? I mean
without any additional change to the class.

Try with gc.get_referrers()

But I saw in the help that we should "Avoid using get_referrers() for
any purpose other than debugging. "

Yes - so what do you want to do actually?

--
Gabriel Genellina

[Tommy Nordgren]

On 17 maj 2008, at 01.44, Terry wrote:

Hi,

Is there a simple way to get all the instances of one class? I mean
without any additional change to the class.

br, Terry
--
http://mail.python.org/mailman/listinfo/python-list

class MyClass : a_base_class
memberlist=[]

# Insert object in memberlist when created;
# note: objects won't be garbage collected until removed from
memberlist.
-------------------------------------
This sig is dedicated to the advancement of Nuclear Power
Tommy Nordgren
to************@comhem.se

[Terry]

On May 18, 11:35 pm, "Diez B. Roggisch" <[e-mail]:

Terry schrieb:

On May 17, 8:04 am, "Gabriel Genellina" <[e-mail]>
wrote:

En Fri, 16 May 2008 20:44:00 -0300, Terry <[e-mail]>
escribió:

>Is there a simple way to get all the instances of one class? I mean
without any additional change to the class.
Try with gc.get_referrers()

pyimport gc
pyclass A(object): pass
...
pya,b,c = A(),A(),A()
pyA
<class __main__.A at 0x00A3F4E0>
pyfor item in gc.get_referrers(A): print type(item)
...
<type 'getset_descriptor'>
<type 'getset_descriptor'>
<type 'tuple'>
<class '__main__.A'>
<class '__main__.A'>
<class '__main__.A'>
<type 'dict'>
<type 'dict'>

We need to filter that list, keeping only A's instances:

py[item for item in gc.get_referrers(A) if isinstance(item,A)]
[<__main__.A object at 0x00A40DC8>, <__main__.A object at 0x00A40DF0>,
<__main__.A object at 0x00A40E18>]

--
Gabriel Genellina

But I saw in the help that we should "Avoid using get_referrers() for
any purpose other than debugging. "

Yes, because using it do is very resource-consuming and shouldn't be
done. Why don't you tell us what you are after here & then we might come
up with a better solution?

Diez

I'm developing a message/state_machine based python program (I'm not
using stackless, plan to move to it later).
I want to collect all the state_machines (threads) and send them
'tick' message or 'quit' message.

Now I'm using a static member to collect the machines, just wonderring
if python already provide something like this.

[Matt Nordhoff]

Tommy Nordgren wrote:

class MyClass : a_base_class
memberlist=[]

# Insert object in memberlist when created;
# note: objects won't be garbage collected until removed from memberlist.

Just to say, if you wanted to go about it that way, you could avoid the
garbage collection problem by using weakrefs:

<http://docs.python.org/lib/module-weakref.html>
--

[Nick Craig-Wood]

Matt Nordhoff <mn*******@mattnordhoff.comwrote:

Tommy Nordgren wrote:

class MyClass : a_base_class
memberlist=[]

# Insert object in memberlist when created;
# note: objects won't be garbage collected until removed from memberlist.

Just to say, if you wanted to go about it that way, you could avoid the
garbage collection problem by using weakrefs:

<http://docs.python.org/lib/module-weakref.html>

Eg...

from weakref import WeakKeyDictionary

class Test(object):
_instances = WeakKeyDictionary()
def __init__(self):
self._instances[self] = True
# your normal init stuff here
@classmethod
def instances(cls):
return cls._instances.keys()

print Test.instances()
a = Test()
b = Test()
print Test.instances()
del a
print Test.instances()
del b
print Test.instances()

.....

Which prints

[]
[<__main__.Test object at 0xb7d4eb6c>, <__main__.Test object at 0xb7d4eb4c>]
[<__main__.Test object at 0xb7d4eb6c>]
[]
--
Nick Craig-Wood <ni**@craig-wood.com-- http://www.craig-wood.com/nick