title: How to save very large ndarray to disk?
body: <p>How to save very large ndarray to disk?</p>
  
  <p>Please note, that any solution, including duplicating of data is not acceptable.</p>
  
  <p>For example, this code</p>
  
  <pre><code>x = pandas.HDFStore("some_file.hdf")
  x.append("a", pandas.DataFrame(a))
  </code></pre>
  
  <p>includes </p>
  
  <pre><code>pandas.DataFrame(a)
  </code></pre>
  
  <p>which unapprovable duplicates memory usage.</p>
  
  <p>Obvious code</p>
  
  <pre><code>pickle.dump(a, f)
  </code></pre>
  
  <p>hangs.</p>