title: Pandas dataframe drop columns with no header
body: <p>What's the most pythonic place to drop the columns in a dataframe where the header row is NaN?  Preferably inplace.</p>
  
  <p>There may or may not be data in the column.</p>
  
  <pre><code>df = pd.DataFrame({'col1': [1,2,np.NaN], 'col2': [4,5,6], np.NaN: [7,np.NaN,9]})
  df.dropna(axis='columns', inplace=True)  
  </code></pre>
  
  <p>Doesn't do it as it looks at the data in the column.</p>
  
  <p>Wanted output </p>
  
  <pre><code>df = pd.DataFrame({'col1': [1,2,np.NaN], 'col2': [4,5,6]})
  </code></pre>
  
  <p>Thanks in advance for the replies.</p>