title: Why function shows none for more output when using insert() method in lists in Python?
body: <p>I am using function to insert method to add a value in list as given below:
  1. insert_value.py file as given below:</p>
  
  <pre><code>def insert_value(my_list, value, insert_position):
  
    str_list3 = ['one','three','four', 'five', 'six']
    str_list4 = ['i', 't']
  
    if my_list == str_list3:
  
          front = my_list[:insert_position]
          back = my_list[insert_position:]
          return front + [value] + back
  
    elif my_list == str_list4:
  
          front = my_list[:insert_position]
  
          back = my_list[insert_position:]
  
          a= front +[value]+ back
  
          return a
  </code></pre>
  
  <ol start="2">
  <li><p>insert_value_test_file.py as given below:</p>
  
  <pre><code>import insert_value
  print("\ninsert_value Test")
  str_list3 = ['one','three','four', 'five', 'six']
  
  new_list = insert_value.insert_value(str_list3, 'two', 1)
  
  print(new_list)
  
  str_list4 = ['i', 't']
  
  str_list4 = insert_value.insert_value(str_list4, 'p', 0)
  
  print(str_list4)
  
  str_list4 = insert_value.insert_value(str_list4, 's', -1)
  
  print(str_list4)
  
  str_list4 = insert_value.insert_value(str_list4, 's', 7)
  
  print(str_list4)
  </code></pre></li>
  </ol>
  
  <p>when running this file my output comes as :</p>
  
  <blockquote>
    <p>insert_value Test ['one', 'two', 'three', 'four', 'five', 'six'] ['p',
    'i', 't'] None None</p>
  </blockquote>
  
  <p>Why None ???? for other inputs in str_list4.</p>