title: Logical operators for Boolean indexing in Pandas
body: <p>I'm working with a Boolean index in Pandas.</p>
  <p>The question is why the statement:</p>
  <pre><code>a[(a['some_column']==some_number) &amp; (a['some_other_column']==some_other_number)]
  </code></pre>
  <p>works fine whereas</p>
  <pre><code>a[(a['some_column']==some_number) and (a['some_other_column']==some_other_number)]
  </code></pre>
  <p>exits with error?</p>
  <p>Example:</p>
  <pre><code>a = pd.DataFrame({'x':[1,1],'y':[10,20]})
  
  In: a[(a['x']==1)&amp;(a['y']==10)]
  Out:    x   y
       0  1  10
  
  In: a[(a['x']==1) and (a['y']==10)]
  Out: ValueError: The truth value of an array with more than one element is ambiguous.     Use a.any() or a.all()
  </code></pre>