title: NetworkX: how to add weights to an existing G.edges()?
body: <p>Given any graph G created in NetworkX, I want to be able to assign some weights to  G.edges() <strong>after</strong> the graph is created. The graphs involved are grids, erdos-reyni, barabasi-albert, and so forth. </p>
  
  <p>Given my <code>G.edges()</code>:</p>
  
  <pre><code>[(0, 1), (0, 10), (1, 11), (1, 2), (2, 3), (2, 12), ...]
  </code></pre>
  
  <p>And my <code>weights</code>:</p>
  
  <pre><code>{(0,1):1.0, (0,10):1.0, (1,2):1.0, (1,11):1.0, (2,3):1.0, (2,12):1.0, ...}
  </code></pre>
  
  <p><strong>How can I assign each edge the relevant weight?</strong> In this trivial case all weights are 1.</p>
  
  <p>I've tried to add the weights to G.edges() directly like this</p>
  
  <pre><code>for i, edge in enumerate(G.edges()):
      G.edges[i]['weight']=weights[edge]
  </code></pre>
  
  <p>But I get this error:</p>
  
  <pre><code>---------------------------------------------------------------------------
  TypeError                                 Traceback (most recent call last)
  &lt;ipython-input-48-6119dc6b7af0&gt; in &lt;module&gt;()
       10 
       11 for i, edge in enumerate(G.edges()):
  ---&gt; 12     G.edges[i]['weight']=weights[edge]
  
  TypeError: 'instancemethod' object has no attribute '__getitem__'
  </code></pre>
  
  <p><strong>What's wrong?</strong> Since <code>G.edges()</code> is a list, why can't I access its elements as with any other list?</p>