"""
This example shows how to read and write variable-length string datatypes to a
dataset.  The program first writes strings to a dataset with a dataspace of
DIM0, then closes the file.  Next, it reopens the file, reads back the data,
and outputs it to the screen.
"""
import sys

import numpy as np
import h5py

FILE = "h5ex_t_vlstring.h5"
DATASET = "DS1"
ATTRIBUTE = "A1"

# Strings are handled very differently between python2 and python3.
if sys.hexversion >= 0x03000000:
    FILE = FILE.encode()
    DATASET = DATASET.encode()
    ATTRIBUTE = "A1".encode()

DIM0 = 4

def run():
    # The "write" data must be a numpy array for variable length strings,
    # not a list.  
    #
    # Does this mean that we can use "|O"?
    wdata = np.empty((DIM0,), "|O")
    wdata[0] = "Parting"
    wdata[1] = "is such"
    wdata[2] = "sweet"
    wdata[3] = "sorrow"

    # Create a new file using the default properties.
    fid = h5py.h5f.create(FILE)

    # Create the file and memory datatypes.  
    filetype = h5py.h5t.FORTRAN_S1.copy()
    filetype.set_size(h5py.h5t.VARIABLE)
    memtype = h5py.h5t.C_S1.copy()
    memtype.set_size(h5py.h5t.VARIABLE)

    # Create the dataspace.  No maximum size parameter needed.
    space = h5py.h5s.create_simple((DIM0,))

    # Create the dataset and write the string data to it.
    dset = h5py.h5d.create(fid, DATASET, filetype, space)
    dset.write(h5py.h5s.ALL, h5py.h5s.ALL, wdata)

    # Explicitly close and release resources.
    del space
    del dset
    del fid

    # Open file and dataset using the default properties.
    fid = h5py.h5f.open(FILE)
    dset = h5py.h5d.open(fid, DATASET)

    rdata = np.empty((DIM0,), dtype="|O")
    dset.read(h5py.h5s.ALL, h5py.h5s.ALL, rdata)

    # Output the data to the screen.
    print("%s:" % DATASET)
    print(rdata)


if __name__ == "__main__":
    run()