title: Can't remove duplicates from DataFrame with drop_duplicates
body: <p>So I am using DataFrame from Pandas, python.</p>
  
  <p>The dataframe, I will be referring to was created by the following way:</p>
  
  <pre><code>search = DataFrame([[262,'ny', '20'],[515,'paris','19'],[669,'ldn','10'], [669,'ldn', 10],[669,'ldn',5]],columns = ['subscriber_id','location','radius' ])
  
  title = DataFrame([[262,'director'],[515,'artist'],[669,'scientist']],columns = ['subscriber_id','title' ])
  </code></pre>
  
  <p>Both the title and search DataFrames are then merged. </p>
  
  <pre><code>mergedTable = merge(title, search, on='subscriber_id', how= 'outer')
  </code></pre>
  
  <p>This forms the dataframe:</p>
  
  <pre><code>   subscriber_id      title location radius
  0            262   director       ny     20
  1            515     artist    paris     19
  2            669  scientist      ldn     10
  3            669  scientist      ldn     10
  4            669  scientist      ldn      5
  </code></pre>
  
  <p>As we can see it has been merged correctly, so we now have data for a subscriber in multiple rows dependent on their searches. </p>
  
  <p>Now I do not want to get rid of the subscribers having multiple rows with different values, but I do want to get rid of duplicate rows. </p>
  
  <p>This is the desired final result:</p>
  
  <pre><code>   subscriber_id      title location radius
  0            262   director       ny     20
  1            515     artist    paris     19
  2            669  scientist      ldn     10
  4            669  scientist      ldn      5
  </code></pre>
  
  <p>The row 3, a duplicate of row 2, is removed. </p>
  
  <p>I have been researching this and it seems that drop_duplicates() should work, i.e.</p>
  
  <pre><code>mergedTable.drop_duplicates()
  </code></pre>
  
  <p>But this doesn't work, rows are not removed. Any tips/solutions available?</p>