how to read Mat v7.3 files in python ？

Question

I am trying to read the mat file given in the following website, ufldl.stanford.edu/housenumbers, in the file train.tar.gz, there is a mat file named digitStruct.mat.

when i used scipy.io to read the mat file, it alerts me with the message ' please use hdf reader for matlab v7.3 files '.

the original matlab file is provided as below

load digitStruct.mat
for i = 1:length(digitStruct)
    im = imread([digitStruct(i).name]);
    for j = 1:length(digitStruct(i).bbox)
        [height, width] = size(im);
        aa = max(digitStruct(i).bbox(j).top+1,1);
        bb = min(digitStruct(i).bbox(j).top+digitStruct(i).bbox(j).height, height);
        cc = max(digitStruct(i).bbox(j).left+1,1);
        dd = min(digitStruct(i).bbox(j).left+digitStruct(i).bbox(j).width, width);

        imshow(im(aa:bb, cc:dd, :));
        fprintf('%d\n',digitStruct(i).bbox(j).label );
        pause;
    end
end

as shown above, the mat file has the key 'digitStruct', and within 'digitStruct', key 'name' and 'bbox' can be found, I used h5py API to read the file.

import h5py
f = h5py.File('train.mat')
print len( f['digitStruct']['name'] ), len(f['digitStruct']['bbox']   )

I can read the array, however when I loop though the array, how can I read each item?

for i in f['digitStruct']['name']:
    print i # only print out the HDF5 ref

Answer 1

Writing in Matlab:

test = {'Hello', 'world!'; 'Good', 'morning'; 'See', 'you!'};
save('data.mat', 'test', '-v7.3') % v7.3 so that it is readable by h5py

Reading in Python (works for any number or rows or columns, but assumes that each cell is a string):

import h5py
import numpy as np

data = []
with h5py.File("data.mat") as f:
    for column in f['test']:
        row_data = []
        for row_number in range(len(column)):            
            row_data.append(''.join(map(unichr, f[column[row_number]][:])))   
        data.append(row_data)

print data
print np.transpose(data)

Output:

[[u'Hello', u'Good', u'See'], [u'world!', u'morning', u'you!']]

[[u'Hello' u'world!']
 [u'Good' u'morning']
 [u'See' u'you!']]