There are various mesh formats available for representing unstructured meshes.
meshio can read and write all of the following and smoothly converts between
them:

Abaqus (.inp), ANSYS msh (.msh), AVS-UCD (.avs), CGNS (.cgns), DOLFIN XML
(.xml), Exodus (.e, .exo), FLAC3D (.f3grid), H5M (.h5m), Kratos/MDPA (.mdpa),
Medit (.mesh, .meshb), MED/Salome (.med), Nastran (bulk data, .bdf, .fem, .nas),
Netgen (.vol, .vol.gz), Neuroglancer precomputed format, Gmsh (format versions
2.2, 4.0, and 4.1, .msh), OBJ (.obj), OFF (.off), PERMAS (.post, .post.gz,
.dato, .dato.gz), PLY (.ply), STL (.stl), Tecplot .dat, TetGen .node/.ele, SVG
(2D output only) (.svg), SU2 (.su2), UGRID (.ugrid), VTK (.vtk), VTU (.vtu), WKT
(TIN) (.wkt), XDMF (.xdmf, .xmf).

It also installs a plug-in to let you open all meshio-supported files in
ParaView.

See also <https://pypi.org/project/meshio/>.