title: Pandas Python: Concatenate dataframes having same columns
body: <p>I have 3 dataframes having the same column names as each other.
  Say :</p>
  
  <pre><code>df1
  column1   column2   column3
  a         b         c
  d         e         f
  
  
  df2
  column1   column2   column3
  g         h         i
  j         k         l
  
  
  df3
  column1   column2   column3
  m         n         o
  p         q         r
  </code></pre>
  
  <p>Each dataframe has different values but the same columns.
  I tried append and concat, as well as merge outer but had errors.
  Here's what I tried:</p>
  
  <p><code>df_final = df1.append(df2, sort=True,ignore_index=True).append2(df3, sort=True,ignore_index=True)</code></p>
  
  <p>I also tried:
      <code>df_final = pd.concat([df1, df2, df3], axis=1)</code></p>
  
  <p>But I get this error: 
  <code>AssertionError: Number of manager items must equal union of block items# manager items: 61, # tot_items: 62</code></p>
  
  <p>I've googled the error but I can't seem to understand why it's happening in my case.
  Any guidance is much appreciated!</p>