title: Size of networkx.Graph() object?
body: <p>I have pandas dataframe with 2 columns: <code>col1</code>, <code>col2</code>. 
  <code>sys.getsizeof(dataframe)</code> shows 495137153 bytes. </p>
  
  <p>Then i grow a graph:</p>
  
  <pre><code>G = networkx.Graph()
  G.add_edges_from(zip(data['col1'], data['col2']))
  </code></pre>
  
  <p>And now i want to check size of my graph, but <code>sys.getsizeof(G)</code> show 64 bytes</p>
  
  <p>How to get real size of object G?</p>
  
  <p>Update: I checked size of <code>G.edges</code> + size <code>G.nodes</code>, it's about 0.2 GB. But growing graph adds ~5 GB to my used RAM. Why so?</p>