title: merge multiple dataframe with specified suffix
body: <p>I implemented to merge multiple dataframe referring to <a href="https://stackoverflow.com/questions/44327999/python-pandas-merge-multiple-dataframes">this page</a>.<br>
  What I want to do is also specify the suffix for each dataframe like below.<br>
  However, I get <code>ValueError: too many values to unpack (expected 2)</code>.<br>
  I understand that giving the tuple longer than 2 for suffix is causing this problem. But I have no idea how I can write code to fix this problem.<br>
  Can anyone tell me how to write?  </p>
  
  <pre><code>def agg_df(dfList, suffix):
      temp=reduce(lambda left, right: pd.merge(left, right, left_index=True, right_index=True, 
                                               how='outer', suffixes=suffix), dfList)
      return temp
  
  df=agg_df([df_cool, df_light, df_sp, df_hvac], ('_chiller', '_light', '_sp', '_hvac'))
  </code></pre>