Splitting and Merging a MED file using MEDLoader

import MEDLoader as ml

m0 = ml.MEDCouplingCMesh()
arr = ml.DataArrayDouble(31,1) ; arr.iota(0.)
m0.setCoords(arr,arr)
m0 = m0.buildUnstructured()
m00 = m0[::2]      # Extract even cells
m00.simplexize(0)
m01 = m0[1::2]
m0 = ml.MEDCouplingUMesh.MergeUMeshes([m00,m01])
m0.getCoords()[:] *= 1/15.
m0.setName("mesh")
# Cell field
cellField = ml.MEDCouplingFieldDouble(ml.ON_CELLS, ml.ONE_TIME)
cellField.setTime(5.6,5,6)
cellField.setMesh(m0)
cellField.setName("CellField")
cellField.fillFromAnalytic(1,"exp(-((x-1)*(x-1)+(y-1)*(y-1)))")
cellField.getArray().setInfoOnComponent(0,"powercell [W]")
# Node field
nodeField = ml.MEDCouplingFieldDouble(ml.ON_NODES,ml.ONE_TIME)
nodeField.setTime(5.6,5,6)
nodeField.setMesh(m0)
nodeField.setName("NodeField")
nodeField.fillFromAnalytic(1,"exp(-((x-1)*(x-1)+(y-1)*(y-1)))")
nodeField.getArray().setInfoOnComponent(0,"powernode [W]")
# Splitting
proc0 = m0.getCellsInBoundingBox([(0.,0.4),(0.,0.4)],1e-10)
proc1 = proc0.buildComplement(m0.getNumberOfCells())
#
nodeField0 = nodeField[proc0] ; cellField0 = cellField[proc0] ; cellField0.setMesh(nodeField0.getMesh())
nodeField1 = nodeField[proc1] ; cellField1 = cellField[proc1] ; cellField1.setMesh(nodeField1.getMesh())

proc0_fname = "proc0.med"
ml.WriteField(proc0_fname, nodeField0, True)
ml.WriteFieldUsingAlreadyWrittenMesh(proc0_fname, cellField0)

proc1_fname = "proc1.med"
ml.WriteField(proc1_fname,nodeField1,True)
ml.WriteFieldUsingAlreadyWrittenMesh(proc1_fname,cellField1)
#
# Merging - Sub-optimal method
#
cellField0_read = ml.ReadFieldCell("proc0.med","mesh",0,"CellField",5,6)
cellField1_read = ml.ReadFieldCell("proc1.med","mesh",0,"CellField",5,6)
cellField_read = ml.MEDCouplingFieldDouble.MergeFields([cellField0_read,cellField1_read])
cellFieldCpy = cellField.deepCopy()
cellFieldCpy.substractInPlaceDM(cellField_read,10,1e-12)
cellFieldCpy.getArray().abs()
print cellFieldCpy.getArray().isUniform(0.,1e-12)
#
nodeField0_read = ml.ReadFieldNode("proc0.med","mesh",0,"NodeField",5,6)
nodeField1_read = ml.ReadFieldNode("proc1.med","mesh",0,"NodeField",5,6)
nodeField_read = ml.MEDCouplingFieldDouble.MergeFields([nodeField0_read, nodeField1_read])
nodeField_read.mergeNodes(1e-10)
nodeFieldCpy = nodeField.deepCopy()
nodeFieldCpy.mergeNodes(1e-10)
nodeFieldCpy.substractInPlaceDM(nodeField_read,10,1e-12)
print nodeFieldCpy.getArray().isUniform(0.,1e-12)
#
# Merging - Optimal method
#
fileNames = ["proc0.med","proc1.med"]
msML = [ml.MEDFileMesh.New(fname) for fname in fileNames]
fsML = [ml.MEDFileFields.New(fname) for fname in fileNames]
mergeMLMesh = ml.MEDFileUMesh()
mergeMLFields = ml.MEDFileFields()
for lev in msML[0].getNonEmptyLevels():
        o2nML = len(msML[0].getNonEmptyLevels())*[None]
        cs = [mML.getCoords() for mML in msML]
        mergeMLMesh.setCoords(ml.DataArrayDouble.Aggregate(cs))
        ms = [mML.getMeshAtLevel(lev) for mML in msML]
        m = ml.MEDCouplingUMesh.MergeUMeshes(ms) ; m.setCoords(mergeMLMesh.getCoords())
        o2nML[lev] = m.sortCellsInMEDFileFrmt()
        mergeMLMesh.setMeshAtLevel(lev,m)
        pass

for fieldName in fsML[0].getFieldsNames():
        fmts = [fML[fieldName] for fML in fsML]
        mergeField = ml.MEDFileFieldMultiTS()
        for dt,it,tim in fmts[0].getTimeSteps():
                fts = [fmt[dt,it] for fmt in fmts]
                arrs = len(fts)*[None]
                for typp in fts[0].getTypesOfFieldAvailable():
                        arr1s = []
                        if typp == ml.ON_CELLS:
                                for ft in fts:
                                        for geoTyp,smth in ft.getFieldSplitedByType():
                                                if geoTyp != ml.NORM_ERROR:
                                                        smth1 = filter(lambda x:x[0] == ml.ON_CELLS,smth)
                                                        arr2s = [ft.getUndergroundDataArray()[elt[1][0]:elt[1][1]] for elt in smth1]
                                                        arr1s.append(ml.DataArrayDouble.Aggregate(arr2s))
                                                        pass
                                                pass
                                        pass
                                pass
                        else:
                                for ft in fts:
                                        smth = filter(lambda x:x[0] == ml.NORM_ERROR,ft.getFieldSplitedByType())
                                        arr2 = ml.DataArrayDouble.Aggregate([ft.getUndergroundDataArray()[elt[1][0][1][0]:elt[1][0][1][1]] for elt in smth])
                                        arr1s.append(arr2)
                                        pass
                                pass
                        arr = ml.DataArrayDouble.Aggregate(arr1s)
                        if typp == ml.ON_CELLS:
                             arr.renumberInPlace(o2nML[lev])
                        mcf = ml.MEDCouplingFieldDouble(typp,ml.ONE_TIME) ; mcf.setName(fieldName) ; mcf.setTime(tim,dt,it) ; mcf.setArray(arr)
                        mcf.setMesh(mergeMLMesh.getMeshAtLevel(lev)) ; mcf.checkConsistencyLight()
                        mergeField.appendFieldNoProfileSBT(mcf)
                        pass
                pass
        mergeMLFields.pushField(mergeField)
        pass
mergeMLMesh.write("merge.med",2)
mergeMLFields.write("merge.med",0)