title: Python - sparse vectors/distance calculation
body: <p>I'm looking for dynamically growing vectors in Python, since I don't know their length in advance. In addition, I would like to calculate distances between these sparse vectors, preferably using the distance functions in scipy.spatial.distance (although any other suggestions are welcome). Any ideas how to do this? (Initially, it doesn't need to be efficient.)</p>
  
  <p>Thanks a lot in advance!</p>