title: Filering columns based on Row values in Pandas
body: <p>I can filter rows based on a column value, using a boolean series.</p>
  
  <pre><code>import pandas as pd
  import numpy as np
  from numpy.random import randn
  df = pd.DataFrame(randn(5,4), ['A', 'B', 'C', 'D', 'E'], ['W','X','Y','Z'])
  
  &gt;&gt;&gt; df[df['W'] &lt; 0]
            W         X         Y         Z
  A -1.080180 -0.512936  0.810030  0.135316
  D -0.713363  0.376887 -0.334995  0.864555
  </code></pre>
  
  <p>How can I filter rows based on a boolean series, how can I filter column based on a column boolean series?  something like this.</p>
  
  <pre><code>df[df.loc['A'] &gt; 1] ##It's wrong syntax I know. 
  </code></pre>