title: numpy .npz load returns BadZipfile: File is not a zip file after a certain size
body: <p>I am saving a large numpy array of shape (40,000, 450, 600, 3).</p>
  
  <p>The array is built by a <code>for</code> loop that converts jpg images to (450, 600, 3) ndarrays and appending the array to the 4 dimensional array and saving it using the <code>numpy.savez_compressed</code> function.</p>
  
  <p>for the first few hundred iterations the <code>numpy.load('file.npz')</code> function works fine and I am able to recover my saved npz file. But at some point I get this error:</p>
  
  <pre><code>Traceback (most recent call last):
  File "script.py", line 14, in &lt;module&gt;
  numpycom = np.load('img_one.npz')
  File "/home/name/.local/lib/python2.6/site-  
  packages/numpy/lib/npyio.py", line 373, in load
  return NpzFile(fid, own_fid=own_fid)
  File "/home/name/.local/lib/python2.6/site- 
  packages/numpy/lib/npyio.py", line 185, in __init__
  _zip = zipfile_factory(fid)
  File "/home/name/.local/lib/python2.6/site-
  packages/numpy/lib/npyio.py", line 124, in zipfile_factory
  return zipfile.ZipFile(*args, **kwargs)
  File "/usr/lib64/python2.6/zipfile.py", line 696, in __init__
  self._GetContents()
  File "/usr/lib64/python2.6/zipfile.py", line 716, in _GetContents
  self._RealGetContents()
  File "/usr/lib64/python2.6/zipfile.py", line 728, in _RealGetContents
  raise BadZipfile, "File is not a zip file"
  zipfile.BadZipfile: File is not a zip file
  Exception AttributeError: "'NpzFile' object has no attribute 'zip'" in 
  &lt;bound method NpzFile.__del__ of &lt;numpy.lib.npyio.NpzFile object at 
  0x2fe4110&gt;&gt; ignored
  </code></pre>
  
  <p>Thank you for any help!</p>