title: Append result of variable to a list
body: <p>I am trying to add the result of a variable <code>f</code> to the end of a list <code>list_name</code>. However, when I try to do this I get the following error:</p>
  
  <pre><code>list_name.append[f]  
  </code></pre>
  
  <p>TypeError: 'builtin_function_or_method' object is not subscriptable</p>
  
  <p>What am I doing wrong?</p>