title: compressing array with pytables
body: <p>I am trying to compress my array like this</p>
  
  <pre><code>import numpy as np
  import tables
  from contextlib import closing
  
  FILTERS = tables.Filters(complib='zlib', complevel=5)
  
  data = np.zeros(10**7)
  
  with closing(tables.open_file('compressed', mode='w', filters=FILTERS)) as hdf:
      hdf.create_array('/', 'array', obj=data)
  
  with closing(tables.open_file('uncompressed', mode='w')) as hdf:
      hdf.create_array('/', 'array', obj=data)
  </code></pre>
  
  <p>but it does not work at all</p>
  
  <pre><code>-rw-rw-r-- 1 user user 80002360 2013-11-21 15:27 compressed
  -rw-rw-r-- 1 user user 80002304 2013-11-21 15:28 uncompressed
  </code></pre>
  
  <p>Am I doing something wrong here?</p>