Write numpy array as scalar to a HDF5 file.

h5_write_array_as_scalar.py

#!/usr/bin/env python3

import h5py
import numpy as np

with h5py.File("test.h5", "w") as f:
    # A is in SIMPLE DataSpace
    f["A"] = np.array([1, 2])

    # B is in SCALAR DataSpace
    ds    = f.create_dataset(name="B", shape=(), dtype=np.dtype(("<u8", (2,))))
    data  = np.array([1, 2])
    space = h5py.h5s.ALL
    tid   = h5py.h5t.py_create(np.dtype(("<u8", (2,))))
    ds.id.write(space, space, data, mtype=tid)

Example output:

HDF5 "test.h5" {
GROUP "/" {
   DATASET "A" {
      DATATYPE  H5T_STD_I64LE
      DATASPACE  SIMPLE { ( 2 ) / ( 2 ) }
      DATA {
      (0): 1, 2
      }
   }
   DATASET "B" {
      DATATYPE  H5T_ARRAY { [2] H5T_STD_U64LE }
      DATASPACE  SCALAR
      DATA {
      (0): [ 1, 2 ]
      }
   }
}
}