title: How to remove rows with null values from kth column onward in python
body: <p>I need to remove all rows in which elements from column 3 onwards are all NaN</p>
  
  <pre><code>df = DataFrame(np.random.randn(6, 5), index=['a', 'c', 'e', 'f', 'g','h'], columns=['one', 'two', 'three', 'four', 'five'])
  
  df2 = df.reindex(['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h'])
  df2.ix[1][0] = 111
  df2.ix[1][1] = 222
  </code></pre>
  
  <p>In the example above, my final data frame would not be having rows 'b' and 'c'. </p>
  
  <p>How to use <code>df.dropna()</code> in this case?</p>