[vtkusers] Python wrapping a custom class

[Kit Chambers]

That works. Discovered I  can still use the boost:python for storage containers as long as the methods pass PyObject pointers.

class VTK_EXPORT vtkImageDataDict: public vtkImageData
{
public:

  vtkTypeMacro(vtkImageDataDict, vtkImageData);

  // New method
  static vtkImageDataDict *New();

  // Python dictionary
  boost::python::dict m_dict;

  // test function to set the dictionary
  void test_set_dict();

  // prints the dictionary
  void printImageDict();

  // Dictionary getter - returns Pyobject because of the VTK Parser
  PyObject* getDict(){return (PyObject*)this->m_dict.ptr();}

  // Dictionary setter
  void setDict(PyObject *dd);

};


Thanks 

Kit







> On 1 Aug 2016, at 13:31, David Gobbi <david.gobbi at gmail.com> wrote:
> 
> Try declaring m_dict as a PyObject:
> 
>   PyObject *m_dict;
>   PyObject *getDict();
>   void setDict(PyObject *);
>   
> 
> On Mon, Aug 1, 2016 at 5:55 AM, Kit Chambers <kit.chambers.kc at gmail.com <mailto:kit.chambers.kc at gmail.com>> wrote:
> Hi David/VTK'ers, 
> 
> Following on from my previous email i am now having diffcultly using a more complicated data structure in a derived class. In this case i am trying:
> 
> #include "vtkImageData.h"
> #include <boost/python.hpp>
> 
> class VTK_EXPORT vtkImageDataDict: public vtkImageData
> {
> public:
> 
>   vtkTypeMacro(vtkImageDataDict, vtkImageData);
> 
>   // New method
>   static vtkImageDataDict *New();
> 
>   // Python dictionary
>   boost::python::dict m_dict;
> 
>   // test function to set the dictionary
>   void test_set_dict();
> 
>   // prints the dictionary
>   void printImageDict();
> 
>   // Dictionary getter
>   boost::python::dict getDict(){return this->m_dict;}
> 
>   // Dictionary setter
>   void setDict(boost::python::object dd);
> };
> 
> 
> When I wrap the above class the test_set_dict and printImageDict work fine but the wrapper seems to ignore getDict()
> and setDict(). I assume this is because vtkWrapperPython does not know what to do with boost::python objects. Maybe I am going about this the wrong way? I did try doing the wrapping through boost python rather than VTK but found I ran into compilation issues. 
> 
> Any help would be very much appreciated. 
> 
> Kit
> 
> 
> 
> 
>> On 29 Jul 2016, at 17:07, David Gobbi <david.gobbi at gmail.com <mailto:david.gobbi at gmail.com>> wrote:
>> 
>> Hi Kit,
>> 
>> It's most likely because the class is missing vtkTypeMacro:
>> 
>> vtkTypeMacro(vtkNewData, vtkImageData);
>> 
>>  - David
>> 
>> 
>> On Fri, Jul 29, 2016 at 9:02 AM, Kit Chambers <kit.chambers.kc at gmail.com <mailto:kit.chambers.kc at gmail.com>> wrote:
>> Hi,
>> 
>> I am trying to wrap a custom class derived from vtkImageData in python. And it works except for when i try to access my custom methods. For example:
>> 
>> import vtkNewDataPython as idp
>> 
>> mydata = idp.vtkNewData()
>> 
>> print "\nvtkImageData functionality"
>> mydata.SetDimensions(2,3,1)
>> dims = mydata.GetDimensions()
>> print "image dimensions =",dims
>> print "Number of points: ",mydata.GetNumberOfPoints()
>> print "Number of cells: ",mydata.GetNumberOfCells()
>> 
>> print "\ncustom functionality" 
>> mydata.set_myvalue()
>> print "Myvalue = ", mydata.get_myvalue()
>> 
>> 
>> Produces:
>> vtkImageData functionality
>> image dimensions = (2, 3, 1)
>> Number of points:  6
>> Number of cells:  2
>> 
>> custom functionality
>> Traceback (most recent call last):
>>   File "./pytest.py", line 14, in <module>
>>     mydata.set_myvalue()
>> AttributeError: set_myvalue
>> 
>> 
>> Basically it is doing just fine up until I try to call a custom method
>> 
>> The class looks like this:
>> 
>> #include "vtkImageData.h"
>> 
>> class VTK_EXPORT vtkNewData: public vtkImageData
>> {
>> public:
>>   static vtkNewData *New();
>>   void set_myvalue(){
>> 	  this->myvalue=3;
>>   }
>>   int get_myvalue(){
>> 	  return this->myvalue;
>>   }
>>   int myvalue;
>> };
>> 
>> 
>> The CmakeLists.txt is adapted mostly from https://github.com/paulmelis/vtk-wrapping-example <https://github.com/paulmelis/vtk-wrapping-example> and looks like this
>> 
>> 
>> #######################################
>> # Pre-requisites
>> 
>> # C++11 flags
>> set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -std=c++11")
>> 
>> # VTK
>> find_package(VTK REQUIRED
>>                 vtkCommonCore
>>                 vtkCommonDataModel
>>                 vtkWrappingPythonCore                  
>>             )
>> include(${VTK_USE_FILE})
>> 
>> # Python and vtk wrapping
>> find_package(PythonLibs 2.7 EXACT REQUIRED)
>> include(vtkWrapPython)
>> include_directories("${PYTHON_INCLUDE_PATH}")
>> 
>> #######################################
>> # Building vtkNewData
>> add_library(vtkNewData SHARED vtkNewData.cxx)
>> TARGET_LINK_LIBRARIES(vtkNewData ${VTK_LIBRARIES} )
>> if(APPLE) 
>>     set_target_properties(vtkNewData PROPERTIES SUFFIX ".so")
>> endif()
>> 
>> #######################################
>> # Wrapping vtkNewData
>> vtk_wrap_python3(vtkNewDataPython vtkNewDataPython_SRCS vtkNewData.cxx)
>> 
>> add_library(vtkNewDataPythonD ${vtkNewDataPython_SRCS} vtkNewData.cxx)
>> target_link_libraries(vtkNewDataPythonD         
>>         ${VTK_LIBRARIES}
>>         vtkWrappingPythonCore 
>>         ${VTK_PYTHON_LIBRARIES})
>> 
>> add_library(vtkNewDataPython MODULE vtkNewDataPythonInit.cxx)
>> 
>> set(VTK_MODULES_USED vtkCommonDataModel vtkCommonCore) 
>> set(VTK_PYTHOND_LIBS)
>> foreach(TMP_LIB ${VTK_MODULES_USED})
>>    set(VTK_PYTHOND_LIBS ${VTK_PYTHOND_LIBS} ${TMP_LIB}PythonD)
>> endforeach()  
>> 
>> target_link_libraries(vtkNewDataPython vtkNewDataPythonD ${VTK_PYTHOND_LIBS})
>> 
>> set_target_properties(vtkNewDataPython PROPERTIES PREFIX "")
>> if(WIN32 AND NOT CYGWIN)
>>     set_target_properties(vtkNewDataPython PROPERTIES SUFFIX ".pyd")
>> endif(WIN32 AND NOT CYGWIN)
>> 
>> 
>> I suspect there is something very simple I am missing here but cannot for the life of me think what. Any help would be appreciated.
>> 
>> 
>> Cheers
>> 
>> Kit
>> 
> 
> 

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