title: AttributeError: 'NoneType' object has no attribute 'append' no matter what
body: <p>I'm (trying to) parsing outputs from a software used by my research group and, so far, I was able to iterate, line by line, the lists I need (ok, there is this little annoying empty list [] at the end of the loop). The real problem starts when I try to append the lists I got in each iteration to a big list (a list of lists) so I can work with it outside the loop.</p>
  
  <p>So far, here is the code:</p>
  
  <pre><code>vdf_file_path = "/home/henrique/Coding/Python/VEDA2XLSX/nq1a.vdf"
  
  vdf_big_list = []
  vdf_s_lines_string = """ """
  
  with open(vdf_file_path, "r") as vdf_all_input_lines:
      for vdf_line in vdf_all_input_lines.readlines()[4:]:
          if "Frequencies" in vdf_line:
              break
          else:
              vdf_s_line_fixed = vdf_line.strip()
              vdf_s_lines_list = list(filter(None,vdf_s_line_fixed.split(" ")))
              vdf_big_list = vdf_big_list.append(vdf_s_lines_list)
  </code></pre>
  
  <p>(forgive me for the messy code, I'm still learning)</p>
  
  <p>Then I receive the error:</p>
  
  <pre><code>Traceback (most recent call last):
    File "/home/henrique/Coding/Python/VEDA2XLSX/importvdf.py", line 12, in &lt;module&gt;
      vdf_big_list = vdf_big_list.append(vdf_s_lines_list)
  AttributeError: 'NoneType' object has no attribute 'append'
  </code></pre>
  
  <p>Despite reading the answer provided <a href="https://stackoverflow.com/questions/13555551/attributeerror-nonetype-object-has-no-attribute-append">here</a> and trying several approaches, I'm still unable to understand what is the problem and fix it.</p>
  
  <p>Any advices?</p>
  
  <p><strong>Data Sample</strong>:</p>
  
  <pre><code>abbreviation of: e:\documents\yyyy\yyyyyy-yyyyyy\camb3lyp\dmso\veda\nq1a.ved
  IR spectrum from file: e:\Documents\yyyyyyy\yyyyyyyyy-yyyyyyyy\CAMB3LYP\dmso\Veda\nq1a.out
  diagonality factor = 53.06   &lt;EPm&gt; = 49.71
      IR    RAMAN   CM-1
   245.54  730.41  3538.10   s1 100
     3.93  204.17  3237.13   s6 93
    11.13  477.42  3233.43   s3 14   s5 76
     3.44  136.83  3229.53   s3 -78   s5 15
   262.17  212.10  1672.05   s16 61
   117.64  169.79  1669.31   s17 -64   s41 14
     9.66   60.78  1657.86   s19 -59   s44 10
   981.59 1079.26  1642.51   s18 -56
  1030.99  315.40  1578.03   s37 40   s42 10
   185.95   27.40  1559.81   s37 20   s42 -37
    55.61   10.42  1535.81   s39 -53   s63 14
     4.91    5.16  1507.94   s20 -37   s40 44
    59.12   24.29  1504.96   s47 69   s76 -23
    14.09   29.85  1492.35   s46 -71   s75 22
    19.97    9.49  1487.58   s48 86
    17.93    4.37  1469.24   s21 -39   s43 -27
  </code></pre>