title: Merge dataframes based on column, only keeping first match
body: <p>I have 2 dataframes like the following.</p>
  
  <pre><code>df_1    
  Index   Fruit
  1       Apple
  2       Banana
  3       Peach
  
  df_2    
  Fruit   Taste
  Apple   Tasty
  Banana  Tasty
  Banana  Rotten
  Peach   Rotten
  Peach   Tasty
  Peach   Tasty
  </code></pre>
  
  <p>I want to merge the two dataframes based on <code>Fruit</code> but only keeping the first occurrence of <code>Apple</code>, <code>Banana</code>, and <code>Peach</code> in the second dataframe. The final result should be:</p>
  
  <pre><code>df_output       
  Index   Fruit   Taste
  1   Apple   Tasty
  2   Banana  Tasty
  3   Peach   Rotten
  </code></pre>
  
  <p>Where <code>Fruit</code>, <code>Index</code>, and <code>Taste</code> are column headers. I tried something like <code>df1.merge(df2,how='left',on='Fruit</code> but it created extra rows based on the length of <code>df_2</code></p>
  
  <p>Thanks.</p>