title: How to deal with array of variable size while creating a HDF5 Dataset in Python?
body: <p>How to create a HDF5 dataset when size of one dimension of a multidimensional array is not fixed. I tried the following toy code, but it seems that I am missing some point here.</p>
  
  <pre><code>import numpy as np
  
  import h5py
  
  
  Polyline=h5py.special_dtype(vlen=np.float32)
  
  f=h5py.File('dataset.hdf5', mode='w')
  
  var_features=f.create_dataset('var_features', (10,), dtype=Polyline )
  
  features = np.empty(shape=(10,), dtype=Polyline)
  
  for i in range(10):
  
      a=10+i*2
      features[i]=np.arange(a).reshape(a/2,2) 
  
  var_features[...]=features
  
  print features[0].shape 
  
  print var_features[0].shape
  </code></pre>