title: Python : Change datatype of hdf5 array
body: <p>I have hdf5 array as bellow:</p>
  
  <pre><code>&gt;&gt;&gt; a = np.array([5,8])
  &gt;&gt;&gt; f = h5py.File('try.hdf5')
  &gt;&gt;&gt; f['try'] = a
  &gt;&gt;&gt; f['try']
  &lt;HDF5 dataset "try": shape (2,), type "&lt;i4"&gt;
  </code></pre>
  
  <p>I want to change datatype of <code>f['try']</code> to <code>float64</code>. How to do it? </p>
  
  <p><code>a = a.astype('float64')</code>will do for numpy but I dont know for hdf5.</p>