title: when is h5py useful in storing data?
body: <p>I am using h5py to store data using python</p>
  
  <pre><code>import h5py
  def store(eigenvalues,eigenvectors,name='01_'):
  
          datafile = h5py.File(name+'data.h5', 'w')
  
          datafile['eigenvalues'] = eigenvalues
          datafile['eigenvectors'] = (eigenvectors)
          datafile.close()
          print "Successfully saved eigenvalues and eigenvectors"
  </code></pre>
  
  <p>It is really useful to store these large numbers
  But when trying to store say two columns of data only, I found saving it normal data file is more space efficient.
  Is there a critical data size above which h5py format storage will be more efficient?
  Also is there any other not-obvious advantage of using this format?</p>