title: Reading Text File of Graph data using NetworkX
body: <p>I'm very new to networkX. So having problem in very basic things.</p>
  
  <p>I've network data in the text file in following format:</p>
  
  <pre><code>InNode  OutNode
  
   N1       N5
   N2       N4
   N3       N6
   N2       N2
   N4       N7
  </code></pre>
  
  <p>My questions are the following:</p>
  
  <p>1) How to read the data using networkX, so that I can get the nodes and edges between the graph?</p>
  
  <p>2) How to calculate the self-edge of the network (N2, N2)?</p>
  
  <p>I tried the following code. But it's not giving me the right answer.</p>
  
  <pre><code>import matplotlib
  import networkx as net
  import urllib
  import csv
  
  
  g = net.Graph()
  
  f1 = csv.reader(open("data.txt","rb"))
  
  for row in f1: 
      g.add_nodes_from(row)
  
  len(g)
  
  g.number_of_nodes()
  </code></pre>