h5py, access data in Datasets in SVHN

Question

I want to read the Street View House Numbers (SVHN) Dataset by using h5py

In [117]: def printname(name):
     ...:     print(name)
     ...:

In [118]: data['/digitStruct'].visit(printname)
bbox
name

There are two group in the data, bbox and name, name is the group name corresponding to the file name data, and bbox is the group name corresponding to the width, height, top, left and label data.

How can I visit all the data in name and bbox group?

I have tried with the following code from the Docs, but it just return HDF5 object reference.

In [119]: for i in data['/digitStruct/name']:
     ...:     print(i[0])
     ...:
     ...:
<HDF5 object reference>
<HDF5 object reference>
<HDF5 object reference>
<HDF5 object reference>
<HDF5 object reference>
<HDF5 object reference>

Python version: 3.5 and OS: Windows 10.

Answer 1

I'll answer my question here, after read the docs of h5py, here is my code

def get_box_data(index, hdf5_data):
    """
    get `left, top, width, height` of each picture
    :param index:
    :param hdf5_data:
    :return:
    """
    meta_data = dict()
    meta_data['height'] = []
    meta_data['label'] = []
    meta_data['left'] = []
    meta_data['top'] = []
    meta_data['width'] = []

    def print_attrs(name, obj):
        vals = []
        if obj.shape[0] == 1:
            vals.append(obj[0][0])
        else:
            for k in range(obj.shape[0]):
                vals.append(int(hdf5_data[obj[k][0]][0][0]))
        meta_data[name] = vals

    box = hdf5_data['/digitStruct/bbox'][index]
    hdf5_data[box[0]].visititems(print_attrs)
    return meta_data

def get_name(index, hdf5_data):
    name = hdf5_data['/digitStruct/name']
    return ''.join([chr(v[0]) for v in hdf5_data[name[index][0]].value])

Here the hdf5_data is train_data = h5py.File('./train/digitStruct.mat'), it works fine!

Update

Here is some sample code to use the above two functions

mat_data = h5py.File(os.path.join(folder, 'digitStruct.mat'))
size = mat_data['/digitStruct/name'].size

for _i in tqdm.tqdm(range(size)):
    pic = get_name(_i, mat_data)
    box = get_box_data(_i, mat_data)

The above function shows how to get the name and the bbox data of each entry of the data!