How to directly convert a gmsh-generated mesh in python?

[dominik-kern]

How to generate (gmsh) and convert (meshio) a mesh directly in one python-script, without intermediate file

gmsh.write("temporary.msh")
mesh = meshio.read("temporary.msh")

The function mesh = pygmsh.helpers.extract_to_meshio() seems appropriate, but fails on mesh.write('output.vtu') with

Info: VTU format cannot write cell_sets. Converting them to cell_data...
Traceback (most recent call last):

  File "/tmp/ipykernel_22333/1224015998.py", line 1, in <module>
    MIOmesh.write('test.vtu')

  File "/home/dominik/.local/lib/python3.10/site-packages/meshio/_mesh.py", line 241, in write
    write(path_or_buf, self, file_format, **kwargs)

  File "/home/dominik/.local/lib/python3.10/site-packages/meshio/_helpers.py", line 188, in write
    return writer(filename, mesh, **kwargs)

  File "/home/dominik/.local/lib/python3.10/site-packages/meshio/vtu/_vtu.py", line 644, in write
    mesh.cell_sets_to_data(key)

  File "/home/dominik/.local/lib/python3.10/site-packages/meshio/_mesh.py", line 328, in cell_sets_to_data
    arr[cc] = i

IndexError: index 14 is out of bounds for axis 0 with size 14

Maybe the mesh representation differs between these two tools (meshio, pygmsh) or their versions.