I can't make Basis work on my code

[ElMastro]

Good Afternoon,
Sorry if I post my problem here, but I don't really know where to do anywhere else;
I am trying to build a python script in order to write out the stiffness matrix and the boundaries to use outside scikit-fem;
my code load the mesh:
try: mesh = MeshQuad.load(path) except: print("Error!")
declare the basis, composed from tetragonal elements
basis = Basis(mesh, ElementTetP0())

after this, following the documentation, I tried to assemble the problem with

form_a = BilinearForm(lambda u, v, w: u * v) B = asm(unit_load, basis) A = asm(form_a, basis)
but if I do
np.savetxt("/tmp/bar.csv", B, delimiter=",")
trying to export matrix B with numpy, a vector (1 column) comes out. What shall I do?

Marco

[kinnala]

You are assembling B using unit_load which is a predefined LinearForm. LinearForm becomes 1D vector after assembled. Perhaps you mean to save A instead?

[ElMastro]

Thank you Dr Gustafsson for the quick answer,
I think I understand it better, now. So if I would like to calculate it on 3 dimensions, I believe i should use
B = asm(laplace, basis) which would assemble the Laplace equation on the mesh. If I am not wrong, I could also take out the boundary vector with vector_a1 = mesh.boundaries['Boundary_1']; np.savetxt("v1.csv", vector_a1, delimiter=",");
My problem is that I found what is u in Finding degrees-of-freedom, but I haven't understand what w and v are (unfortunately in my university book there isn't a similar convention)