Meshconnectivity

How can use mesh connectivity in the following code?


def create_mesh(mesh, cell_type, prune_z=False):
    cells = mesh.get_cells_type(cell_type)
    cell_data = mesh.get_cell_data("gmsh:physical", cell_type)
    out_mesh = meshio.Mesh(points=mesh.points, cells={cell_type: cells}, cell_data={"name_to_read":[cell_data]})
    if prune_z:
        out_mesh.prune_z_0()
    return out_mesh


msh = meshio.read("ji-brace-2011.msh")

triangle_mesh = create_mesh(msh, "triangle", True)
line_mesh = create_mesh(msh, "line", True)
meshio.write("mesh.xdmf", triangle_mesh)
meshio.write("mf.xdmf", line_mesh) 

from dolfin import *

mesh=Mesh()
mvc = MeshValueCollection("size_t", mesh, mesh.topology().dim())
with XDMFFile("mesh.xdmf") as infile:
   infile.read(mesh)
   infile.read(mvc, "name_to_read")

cf = cpp.mesh.MeshFunctionSizet(mesh, mvc)

mvc = MeshValueCollection("size_t", mesh, mesh.topology().dim()-1)
with XDMFFile("mf.xdmf") as infile:
    infile.read(mvc, "name_to_read")   
mf = cpp.mesh.MeshFunctionSizet(mesh, mvc) 

geo file is

am = 0.00003;
lm = 0.005;
wp = 0.01;
ds = 0.05;
Point(1) = {0, -0.013, 0, am};
Point(2) = {0.000255, -0.013, 0, am};
Point(3) = {0.000255, wp, 0, am};
Point(4) = {0.00084, wp, 0, am};
Point(5) = {0.00084, 0, 0, am};
Point(6) = {0.0011, 0, 0, am};
Point(7) = {0.0011, ds, 0, lm};
Point(8) = {0.05, ds, 0, lm};
Point(9) = {0.05, -ds, 0, lm};
Point(10) = {0, -ds, 0, lm};
Point(11) = {0.000255, 0, 0, am};
Line(1) = {1, 2};
Line(2) = {2, 11};
Line(3) = {11, 3};
Line(4) = {3, 4};
Line(5) = {4, 5};
Line(6) = {5, 11};
Line(7) = {5, 6};
Line(8) = {6, 7};
Line(9) = {7, 8};
Line(10) = {8, 9};
Line(11) = {9, 10};
Line(12) = {10, 1};
Line Loop(13) = {12, 1, 2, -6, 7, 8, 9, 10, 11};
Plane Surface(14) = {13};
Line Loop(15) = {3, 4, 5, 6};
Plane Surface(16) = {15};
Physical Line(1) = {12};
Physical Line(2) = {9, 10, 11};
Physical Line(4) = {4};
Physical Line(5) = {9, 10, 11};
Physical Surface(2) = {16};
Physical Surface(1) = {14};

You need to be more specific. What kind of mesh connectivity do you want, and what would you like to use it for?
There are already posts regarding how to initialize mesh connectivity in the forum, see for instance:

or

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