"""
This example shows how to read and write data to a dataset.  The
program first writes integers to a dataset with dataspace dimensions
of DIM0xDIM1, 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_d_rdwr.h5"
DATASET = "DS1"

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

DIM0 = 4
DIM1 = 7

def run():

    # Initialize the data.
    wdata = np.zeros((DIM0, DIM1), dtype=np.int32)
    for i in range(DIM0):
        for j in range(DIM1):
            wdata[i][j] = i * j - j

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

    # Create the dataspace.  No maximum size parameter needed.
    dims = (DIM0, DIM1)
    space = h5py.h5s.create_simple(dims)

    # Create the datasets using default properties.
    dset = h5py.h5d.create(fid, DATASET, h5py.h5t.STD_I32LE, space)

    # Write the data to the dataset.
    dset.write(h5py.h5s.ALL, h5py.h5s.ALL, wdata)

    # Close and release resources.
    del dset
    del space
    del fid

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

    # Read the data using default properties.
    rdata = np.zeros((DIM0, DIM1), dtype=np.int32)
    dset.read(h5py.h5s.ALL, h5py.h5s.ALL, rdata)

    print("%s:" % DATASET)
    print(rdata)

if __name__ == "__main__":
    run()