Numpy string types in compound type · Issue #773 · Unidata/netcdf4-python (original) (raw)

I have the following Numpy dtype for an array:

dtype([('Object_type', 'S30'), ('ID', 'S30'), ('Version', '<i4'), ('basis_1', [('x', '<f8'), ('y', '<f8'), ('z', '<f8')]), ('basis_2', [('x', '<f8'), ('y', '<f8'), ('z', '<f8')]), ('centre_point', [('x', '<f8'), ('y', '<f8'), ('z', '<f8')]), ('width', '<f8'), ('height', '<f8'), ('slit_id', 'S30'), ('slit_no', '<i4')])

When I try to create a NetCDF compound type from this dtype, I get the following error:

KeyError Traceback (most recent call last) netCDF4/_netCDF4.pyx in netCDF4._netCDF4._def_compound (netCDF4/_netCDF4.c:51191)()

KeyError: 'S30'

During handling of the above exception, another exception occurred:

ValueError Traceback (most recent call last) in () 20 nc_coord = bolo_group.createCompoundType(cartesian_coord, "COORDINATE") ---> 21 nc_detector = bolo_group.createCompoundType(aperture_dtype_full, "DETECTOR") 22 foil_no = bolo_group.createDimension("foil_no", foils.size)

netCDF4/_netCDF4.pyx in netCDF4._netCDF4.Dataset.createCompoundType (netCDF4/_netCDF4.c:16268)()

netCDF4/_netCDF4.pyx in netCDF4._netCDF4.CompoundType.init (netCDF4/_netCDF4.c:49971)()

netCDF4/_netCDF4.pyx in netCDF4._netCDF4._def_compound (netCDF4/_netCDF4.c:51245)()

ValueError: Unsupported compound type element

During handling of the above exception, another exception occurred:

RuntimeError Traceback (most recent call last) in () 27 nc_slits = sxd_group.createVariable("slits", nc_detector, "slit_no") 28 nc_slits[:] = slits_full ---> 29 nc_slits.units = "mm"

netCDF4/_netCDF4.pyx in netCDF4._netCDF4.Dataset.exit (netCDF4/_netCDF4.c:13090)()

netCDF4/_netCDF4.pyx in netCDF4._netCDF4.Dataset.close (netCDF4/_netCDF4.c:15045)()

RuntimeError: NetCDF: HDF error

I understand that it is not possible to create compound types which include variable-length arrays, but the Numpy '<S30' type should always be 30 bytes, not a variable length. This is actually why I'm using S30 and not U30, since the latter may have multi-byte characters.

Is it possible to add support for the S30 dtype in netcdf4-python? Otherwise, is there another way that I can include fixed length string types in a NetCDF compound type?