title: How do I group lat-lon pairings in a Pandas DataFrame?
body: <p>I have a dataframe that looks like:</p>
  
  <pre><code>lon        lat
  -77.487    39.044
  -77.487    39.044
  -122.031   37.354
  -77.487    39.044
  </code></pre>
  
  <p>I want to group these lon-lat pairings with a resulting count, like so:</p>
  
  <pre><code>lon        lat      count
  -77.487    39.044   3
  -122.031   37.354   1
  </code></pre>
  
  <p>How can I do this? The <code>group()</code> function only appears to allow for grouping by one column.</p>