title: Values in Wrong Columns After Pandas DataFrame.to_csv()
body: <p>I am concatenating two data files using Pandas. The concat is working well but when I write the data back to csv the data loses some coherency:</p>
  
  <pre><code># Define DataFrame 1
  headerList1 = ['A', 'B', 'C', 'D']
  b1 = np.array([[0, 'B_foo', 2, 'D_one'],
                [3, 'B_bar', 5, 'D_two'],
                [6, 'B_cat', 8, 'D_one']])
  df1 = pd.DataFrame(b1, columns=headerList1)
  
  # Define DataFrame 2
  headerList2 = ['C', 'E', 'F', 'G']
  b2 = np.array([[12, 'E_foo', 2, 'G_one'],
                [15, 'E_bar', 5, 'G_two'],
                [19, 'E_cat', 8, 'G_one']])
  df2 = pd.DataFrame(b2, columns=headerList2)
  
  # Concat DataFrames
  df3 = pd.concat([df1, df2], axis=0, ignore_index=True)
  
  # Write to csv
  scratchFile = os.path.join(dir, 'scratch.csv')
  df3.to_csv(scratchFile, index_label=False, ignore_index=True)
  </code></pre>
  
  <p>I am looking for:</p>
  
  <pre><code>  A      B   C      D      E    F      G
    0  B_foo   2  D_one    NaN  NaN    NaN
    3  B_bar   5  D_two    NaN  NaN    NaN
    6  B_cat   8  D_one    NaN  NaN    NaN
  NaN    NaN  12    NaN  E_foo    2  G_one
  NaN    NaN  15    NaN  E_bar    5  G_two
  NaN    NaN  19    NaN  E_cat    8  G_one
  </code></pre>
  
  <p>but get:</p>
  
  <pre><code>A     B     C       D       E       F       G
  0     0     B_foo   2     D_one   Nan     Nan
  1     3     B_bar   5     D_two   Nan     Nan
  2     6     B_cat   8     D_one   Nan     Nan
  3    Nan    Nan     12    Nan     E_foo    2     G_one
  4    Nan    Nan     15    Nan     E_bar    5     G_two
  5    Nan    Nan     19    Nan     E_cat    8     G_one
  </code></pre>
  
  <p>I can almost reach the desired result by removing index_label=False from the to_csv() command but this results in the addition of an undesired index column. </p>
  
  <p>Is there a way to get the desired output without the index column?  Also, of personal interest, why does removing the index_label=False disrupt the column organization?</p>
  
  <p>Thanks!</p>