Transform dolfinx assemble matrix to numpy array

dolfinx
2

You need to supply the full code, as the following works for me:

import dolfinx
import ufl
from ufl import ds, dx, grad, inner

mesh = dolfinx.UnitSquareMesh(dolfinx.MPI.comm_world, 10, 10)
V = dolfinx.FunctionSpace(mesh, ("Lagrange", 1))

u = ufl.TrialFunction(V)
v = ufl.TestFunction(V)
a = inner(grad(u), grad(v)) * dx
A = dolfinx.fem.assemble_matrix(a)
A.assemble()
B = A.convert("dense")
C = A.getDenseArray()
print(C)