title: What is the difference between dataframe.series and dataframe['series']?
body: <p>I just tried sorting my dataframe and used the following function:</p>
  
  <pre><code>df[df.count &gt;= df.count.quantile(.95)]
  </code></pre>
  
  <p>It returned the error:</p>
  
  <pre><code>AttributeError: 'function' object has no attribute 'quantile'
  </code></pre>
  
  <p>But bracketing the series works fine:</p>
  
  <pre><code>df[df['count'] &gt;= df['count'].quantile(.95)]
  </code></pre>
  
  <p>It's not the first time I've gotten different results based on this distinction, but it also usually doesn't happen, and I always thought that these were two identical objects.</p>
  
  <p>Why does this happen? </p>