[vtkusers] release memory allocated in vtk from python

[David Gobbi]

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