title: Getting MemoryError while calling np.vstack()
body: <p>I am working on action recognition in UCF Sport dataset . I have extracted all the features . But I need to keep all those features in a numpy array. </p>
  
  <pre><code>test = []
  train = []
  test.append(allhogs[i])
  test.append(allhogs[i+1])
  vid_descs = []
  print allhogs[i]
  for el in allhogs[0:i]:
      train.append(el)
  for el in allhogs[i+2:]:
     train.append(el)
     feat = s.genfromtxt('/media/prithviraj/Seagate Backup Plus Drive/ucf_sports_feat/' + el)
     # print feat
     k = len(feat)/96
     feat = np.asarray(feat)      
     feat= feat.reshape((k,96))  
     vid_descs.append(feat)
  vid_descs = np.asarray(vid_descs)
  
  all_desc = np.vstack(vid_descs)
  print all_desc.shape
  </code></pre>
  
  <p>I am getting this error :</p>
  
  <pre><code>Traceback (most recent call last):
  File "t.py", line 39, in &lt;module&gt;
  all_desc = np.vstack(vid_descs)
  File "/usr/lib/python2.7/dist-packages/numpy/core/shape_base.py", line 228, in vstack
  return _nx.concatenate([atleast_2d(_m) for _m in tup], 0)
  MemoryError
  </code></pre>
  
  <p>The shape of vid_descs array is (298, 723456, 96). I also saved the vid_descs array and found out that its size is 6 GB. My system's RAM is also 6GB. So should I migrate to a system with higher RAM? Is there any other solution?</p>