[vtkusers] release memory allocated in vtk from python

[José M. Rodriguez Bacallao]

ok, but with a shallow copy, the output will not increment the reader reference?

On Mon, Jul 2, 2012 at 4:02 PM, David Gobbi <david.gobbi at gmail.com> wrote:
> A shallow copy isn't like a weakref.  A shallow copy will copy all the
> arrays from one data object to another data object by reference
> (strong reference, not weak reference).  A deep copy will create new
> arrays and copy all the values from the old arrays.
>
> I'm not sure how much git master will change before it is released, if
> that's what you are asking, but it already has the new pipeline
> features.
>
>  - David
>
> On Mon, Jul 2, 2012 at 1:26 PM, José M. Rodriguez Bacallao
> <jmrbcu at gmail.com> wrote:
>> so, a shallow copy is like a weakref in python no? I don't want to be
>> that minimalist (example 2) because example 2 does not copy any lookup
>> table, etc. How far is the git/master from what would be VTK 6.0?
>>
>> On Mon, Jul 2, 2012 at 2:36 PM, David Gobbi <david.gobbi at gmail.com> wrote:
>>> The original question was asking how to free the reader and keep the
>>> data.  When you do "output=reader.GetOutput()", the output keeps a
>>> reference to the reader, so the reader will not be freed until the
>>> output is freed.  This is why it sometimes make sense to copy the
>>> output into a new vtkImageData object.
>>>
>>> In VTK 6, if you call "output=reader.GetOutput()" then the output does
>>> not keep a reference to the reader, so memory management is a bit
>>> easier.
>>>
>>> Python memory management does what it's supposed to: it deletes
>>> objects that aren't referred to by any other objects.  If an object is
>>> part of a pipeline, it won't be deleted until 1) it is disconnected
>>> from the pipeline or 2) there are no external references to any of the
>>> objects that make up the pipeline.
>>>
>>>  - David
>>>
>>>
>>> On Mon, Jul 2, 2012 at 12:12 PM, Jothybasu Selvaraj <jothybasu at gmail.com> wrote:
>>>> Won't the auto garbage collection/ memory management in python manage this?
>>>>
>>>>
>>>> On Mon, Jul 2, 2012 at 7:05 PM, David Gobbi <david.gobbi at gmail.com> wrote:
>>>>>
>>>>> A shallow copy should be sufficient:
>>>>>
>>>>> def test(filename):
>>>>>    r = vtkgdcm.vtkGDCMImageReader()
>>>>>    r.SetFileName(filename)
>>>>>    r.Update()
>>>>>    img = vtk.vtkImageData()
>>>>>    img.ShallowCopy(r.GetOutput())
>>>>>    return img
>>>>>
>>>>> Or, to be even more minimalist, copy just the pixel data and nothing else:
>>>>>
>>>>> def test(filename):
>>>>>    r = vtkgdcm.vtkGDCMImageReader()
>>>>>    r.SetFileName(filename)
>>>>>    r.Update()
>>>>>    img = vtk.vtkImageData()
>>>>>    img.CopyStructure(r.GetOutput())
>>>>>    img.GetPointData().PassData(r.GetOutput().GetPointData())
>>>>>    return img
>>>>>
>>>>>  - David
>>>>>
>>>>> On Mon, Jul 2, 2012 at 10:17 AM, Jothy <jothybasu at gmail.com> wrote:
>>>>> > I think the first one.
>>>>> >
>>>>> > Jothy
>>>>> >
>>>>> > On 02-Jul-2012, at 5:06 PM, José M. Rodriguez Bacallao
>>>>> > <jmrbcu at gmail.com> wrote:
>>>>> >
>>>>> >> hi folks, how to correctly release memory using vtk from python
>>>>> >> for example, which one of this three code snnipets release the memory
>>>>> >> allocated when reading the file:
>>>>> >>
>>>>> >> def test(filename):
>>>>> >>    r = vtkgdcm.vtkGDCMImageReader()
>>>>> >>    r.SetFileName(filename)
>>>>> >>    r.Update()
>>>>> >>    img = vtk.vtkImageData()
>>>>> >>    img.DeepCopy(r.GetOutput())
>>>>> >>    return img
>>>>> >>
>>>>> >> --------------------------------------------------------------------------
>>>>> >> def test(filename):
>>>>> >>    r = vtkgdcm.vtkGDCMImageReader()
>>>>> >>    r.SetFileName(filename)
>>>>> >>    r.Update()
>>>>> >>    return r.GetOutput()
>>>>> >>
>>>>> >> ---------------------------------------------------------------------------
>>>>> >> r = vtkgdcm.vtkGDCMImageReader()
>>>>> >> r.SetFileName(filename)
>>>>> >> r.Update()
>>>>> >> img = r.GetOutput()
>>>>> >> img = None
>>>>> >> del img
>>>>> >> r = None
>>>>> >> del r