title: Writing 3 python dictionaries to a csv
body: <p>I have 3 dictionaries( 2 of them are setdefault dicts with multiple values)-<br>
  Score_dict-</p>
  
  <pre><code>{'Id_1': [('100001124156327', 0.0),                                                                                                                                                                                                                                                                                
            ('100003643614411',0.0)],
   'Id_2': [('100000435456546',5.7),
            ('100000234354556',3.5)]}
  </code></pre>
  
  <p>post_dict-</p>
  
  <pre><code>{'Id_1':[(+,100004536)],
   'Id_2' :[(-,100035430)]}
  </code></pre>
  
  <p>comment_dict-</p>
  
  <pre><code>{'Id_1':[(+,1023434234)],
   'Id_2':[(-,10343534534)
            (*,1097963644)]}
  </code></pre>
  
  <p>My current approach is to write them into 3 different csv files and then merging them,I want to merge them according to a common first row(ID_row).
  But I am unable to figure out how to merge 3 csv files into a single csv file. Also , Is there any way which I can write all the 3 dictionaries into a single csv without writing them individually.</p>
  
  <p>Output required-</p>
  
  <pre><code>Ids   Score_Ids                Post_Ids      Comment_Ids
  Id_1  100001124156327',0.0     +,100004536   +,1023434234
        100003643614411',0.0
  Id_2  100000435456546',5.7     -,100035430   -,10343534534
        100000234354556',3.5                   *,1097963644                                                                                                               
  </code></pre>
  
  <p>How to do this in a correct way with the best approach?</p>