title: Read bipartite graph
body: <p>I'm trying to read a graph from a .txt file that has the following structure:</p>
  
  <pre><code>115564928125997351000, ah.creativecodeapps.tiempo,1
  117923818995099650007, air.com.agg.popcornmakermarket,-1
  104000841215686444437, air.com.zahdoo.cadie,1
  .
  .
  .
  </code></pre>
  
  <p>I've been using the following command:</p>
  
  <pre><code>g=nx.read_weighted_edgelist('siatoy.txt', delimiter=',',nodetype=str,encoding='utf-8')
  </code></pre>
  
  <p>But when I do <code>g.edges(data=True)</code>, I got this:</p>
  
  <pre><code>[('106784557494786869271', ' com.map2app.U5635321228165120A5661458385862656'),
  ('106784557494786869271',' com.jb.gokeyboard.theme.mzdevelopment.americankeyboard'),
  ('106784557494786869271', ' com.benbasha.whoopeecushion'),
  (' com.airplaneflighttakeoff', '115981152169430603941'),...]
  </code></pre>
  
  <p>But I want to get always the numeric id as the first element of the tuple. Note that this is not happening at the last element of the list I show in the example. </p>
  
  <p>How can I do to get this? I need to iterate over the edges later and I need to take into account the order on the edges, meaning that I need the first element of the tuple to be the numeric id always.</p>
  
  <p>The question is how can I achieve this while reading the graph or after doing it?</p>