title: merging error in pandas
body: <p>I have a dataframes that looks like this:</p>
  
  <p>top_ten_movies:</p>
  
  <pre><code>movieId  count   mean   
  1        247     3.872470
  2        107     3.401869
  6        104     3.884615
  10       122     3.450820
  25       101     3.742574
  32       196     3.923469
  34       148     3.601351
  36       104     3.937500
  39       120     3.550000
  47       201     4.034826
  </code></pre>
  
  <p>movies:</p>
  
  <pre><code>movieId  title                                  genres
  1        Toy Story (1995)                       Adventure
  2        Jumanji (1995)                         Children|Fantasy
  3        Grumpier Old Men (1995)                Comedy|Romance
  4        Waiting to Exhale (1995)               Comedy|Drama|Romance
  5        Father of the Bride Part II (1995)     Comedy
  6        Heat (1995)                            Action|Crime|Thriller
  7        Sabrina (1995)                         Comedy|Romance
  8        Tom and Huck (1995)                    Adventure|Children
  9        Sudden Death (1995)                    Action
  </code></pre>
  
  <p>I need to merge based on the movieId, so:</p>
  
  <pre><code>required_data=pd.merge(top_ten_movies, movies)
  required_data=pd.merge(top_ten_movies, movies, on='movieId', how='outer')
  </code></pre>
  
  <p>Both the statements are throwing the error. Can someone help...?</p>