title: Case insensitive list item comparison python
body: <p>I'm working trough the Python Crash Course book and I am doing this assignment.</p>
  <blockquote>
  <p>Do the following to create a program that simulates how websites ensure that everyone has a unique username.</p>
  <ul>
  <li>Make a list of five or more usernames called <code>current_users</code>.</li>
  <li>Make another list of five usernames called <code>new_users</code>. Make sure one or two of the new usernames are also in the <code>current_users</code> list.</li>
  <li>Loop through the <code>new_users</code> list to see if each new username has already been used. If it has, print a message that the person will need to enter a new username. If a username has not been used, print a message saying that the username is available.</li>
  <li>Make sure your comparison is case insensitive. If <code>'John'</code> has been used, <code>'JOHN'</code> should not be accepted.</li>
  </ul>
  </blockquote>
  <p>I can see if a username in one list is in another with.</p>
  <pre><code>current_users = [&quot;John&quot;, &quot;Admin&quot;, &quot;Jack&quot;, &quot;Ana&quot;, &quot;Natalie&quot;]
  new_users = [&quot;Pablo&quot;, &quot;Donald&quot;, &quot;Calvin&quot;, &quot;Natalie&quot;, &quot;Emma&quot;]
  
  for username in new_users:
      if username in current_users:
          print(&quot;Username unavailable.&quot;)
      else:
          print(&quot;Username available.&quot;)
  </code></pre>
  <p>Now for the case insensitive part I know about the .lower() method, but not sure how to convert a list item to lowercase in the loop. I could do <code>if username.lower() in current_users</code>, which wouldn't work because I need to covert current_users somehow. Is there a better way then just doing <code>.lower()</code> for both lists before the loop.</p>