Reading, Writing a MED file using MEDLoader’s basic API¶
The basic API is incarnated by the MEDLoader class. All methods in that class are static. The sessions of read/write are done on each call of a method.
Objective¶
Write a mesh and a field from scratch, re-read them and compare the result.
Topics covered: * Write using MEDLoader’s basic API * Read using MEDLoader’s basic API
Implementation start¶
To implement this exercise we use the Python scripting language and import the medcoupling Python module.
import medcoupling as mc
Writing/Reading a mesh¶
First of all, creation of a mesh “targetMesh”.
targetCoords=[-0.3,-0.3, 0.2,-0.3, 0.7,-0.3, -0.3,0.2, 0.2,0.2, 0.7,0.2, -0.3,0.7, 0.2,0.7, 0.7,0.7 ]
targetConn=[0,3,4,1, 1,4,2, 4,5,2, 6,7,4,3, 7,8,5,4]
targetMesh=mc.MEDCouplingUMesh.New("MyMesh",2)
targetMesh.allocateCells(5)
targetMesh.insertNextCell(NORM_TRI3,3,targetConn[4:7])
targetMesh.insertNextCell(NORM_TRI3,3,targetConn[7:10])
targetMesh.insertNextCell(NORM_QUAD4,4,targetConn[0:4])
targetMesh.insertNextCell(NORM_QUAD4,4,targetConn[10:14])
targetMesh.insertNextCell(NORM_QUAD4,4,targetConn[14:18])
myCoords=mc.DataArrayDouble.New(targetCoords,9,2)
myCoords.setInfoOnComponents(["X [km]","YY [mm]"])
targetMesh.setCoords(myCoords)
Note
targetMesh is ordered by geometric type.
We are then ready to write it.
mc.WriteUMesh("TargetMesh.med",targetMesh,True)
Then trying to read it.
meshRead=mc.ReadUMeshFromFile("TargetMesh.med",targetMesh.getName(),0)
print("Is the mesh read in file equals targetMesh? %s"%(meshRead.isEqual(targetMesh,1e-12)))
Writing/Reading a field on one time step at once¶
Creation of a vector field “f” on cell supported by “targetMesh”.
f=mc.MEDCouplingFieldDouble.New(ON_CELLS,ONE_TIME)
f.setTime(5.6,7,8)
f.setArray(targetMesh.computeCellCenterOfMass())
f.setMesh(targetMesh)
f.setName("AFieldName")
mc.WriteField("MyFirstField.med",f,True)
Note
Mesh AND Field is written at once into MyFirstField.
Reading into MyFirstField.med
f2=mc.ReadFieldCell("MyFirstField.med",f.getMesh().getName(),0,f.getName(),7,8)
print("Is the field read in file equals f ? %s"%(f2.isEqual(f,1e-12,1e-12)))
Writing/Reading a field on one or many times steps in “multi-session mode”¶
Here contrary to the previous steps, we are going to write in a multi-session mode on the same MED file. First dealing with the mesh.
mc.WriteUMesh("MySecondField.med",f.getMesh(),True)
Then writing only array part of field.
mc.WriteFieldUsingAlreadyWrittenMesh("MySecondField.med",f)
Then put a another time step.
f2=f.clone(True)
f2.getArray()[:]=2.0
f2.setTime(7.8,9,10)
mc.WriteFieldUsingAlreadyWrittenMesh("MySecondField.med",f2)
Now “MySecondField.med” file contains 2 time steps.