"""
This example shows how to read and write float datatypes to an attribute. The
program first writes floats to an attribute with a dataspace 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_t_floatatt.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 = ATTRIBUTE.encode()

DIM0 = 4
DIM1 = 7
DIMS = (DIM0, DIM1)

def run():
    # Initialize the data.
    wdata = np.zeros((DIM0, DIM1), dtype=np.float64)
    for i in range(DIM0):
        for j in range(DIM1):
            wdata[i][j] = i / (j + 0.5) + j

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

    # Create a dataset with a scalar dataspace.
    # The origin C example uses a NULL dataspace, but this does not seem to
    # yet be possible in H5PY.
    space = h5py.h5s.create(h5py.h5s.SCALAR)
    dset = h5py.h5d.create(fid, DATASET, h5py.h5t.STD_I32LE, space)
    dset.write(h5py.h5s.ALL, h5py.h5s.ALL, wdata)
    del space

    # Create the attribute dataspace.  Not supplying a maximum size results
    # in the maximum size being equal to the current size.
    space = h5py.h5s.create_simple(DIMS)

    # Create the attribute and write the floating point data to it.
    # In this example we will save the data as 64 bit little endian
    # IEEE floating point numbers, regardless of the native type.  The
    # HDF5 library automatically converts between different floating point
    # types.
    attr = h5py.h5a.create(dset, ATTRIBUTE, h5py.h5t.IEEE_F64LE, space)
    attr.write(wdata)
            

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

    # Open file and dataset using the default properties.
    fid = h5py.h5f.open(FILE)
    dset = h5py.h5d.open(fid, DATASET)
    attr = h5py.h5a.open(dset, ATTRIBUTE)

    # Get the dataspace and allocate space for the read buffer.
    space = attr.get_space()
    rdata = np.zeros((DIM0, DIM1), dtype=np.float64)

    attr.read(rdata)

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


if __name__ == "__main__":
    run()