Saving dictionary of numpy arrays

Let’s look at a small example:

In [819]: N
Out[819]: 
array([[  0.,   1.,   2.,   3.],
       [  4.,   5.,   6.,   7.],
       [  8.,   9.,  10.,  11.]])

In [820]: data={'N':N}

In [821]: np.save('temp.npy',data)

In [822]: data2=np.load('temp.npy')

In [823]: data2
Out[823]: 
array({'N': array([[  0.,   1.,   2.,   3.],
       [  4.,   5.,   6.,   7.],
       [  8.,   9.,  10.,  11.]])}, dtype=object)

np.save is designed to save numpy arrays. data is a dictionary. So it wrapped it in a object array, and used pickle to save that object. Your data2 probably has the same character.

You get at the array with:

In [826]: data2[()]['N']
Out[826]: 
array([[  0.,   1.,   2.,   3.],
       [  4.,   5.,   6.,   7.],
       [  8.,   9.,  10.,  11.]])