title: Difference between two conditional queries on a pandas dataframe?
body: <p>I was trying to find records based on two conditions on a data frame <code>preg</code></p>
  
  <p>First:</p>
  
  <pre><code>preg[preg.caseid==2298 &amp; preg.pregordr==1]
  </code></pre>
  
  <p>This throws and error that truth value of a series is ambiguous.
  Why?</p>
  
  <p>Second:
  But this one works!</p>
  
  <pre><code>preg[(preg.caseid==2298) &amp; (preg.pregordr==1)]
  </code></pre>
  
  <p>So what exactly is the difference between the two?</p>