title: ignoring null value columns in python
body: <p>I Have a .txt file which has three columns in it.</p>
  
  <pre><code>id      ImplementationAuthority.email   AssignedEngineer.email
  ALU02034116     bin.a.chen@shan.cn bin.a.chen@ell.com.cn
  ALU02035113                                     Guolin.Pan@ell.com.cn
  ALU02034116     bin.a.chen@ming.com.cn Guolin.Pan@ell.com.cn
  ALU02022055     fria-sha-qdv@list.com
  ALU02030797     fria-che-equipment-1@phoenix.com    Balagopal.Velusamy@phoenix.com
  </code></pre>
  
  <p>I need to create two lists which comprises of values under the column Implementation Authority.mail and Assigned Engineer.mail. It works perfectly when columns have compltete values (i.e no null values). The values got mixed when column contains null values. </p>
  
  <pre><code>aengg=[]
  iauth=[]
  
  with open('test.txt') as f:
   for i, row in enumerate(f):
    columns = row.split()
    if len(columns) == 3:
     aengg.append(columns[2])
     iauth.append(columns[1])
  
   print aengg
   print iauth
  </code></pre>
  
  <p>I tried it with this code and it is perfectly worked for complete column values.
  Can anyone please tell me a solution for null values?</p>