title: checking if a letter is present in a string in python
body: <p>How can I check if the letter "N" is present in a string.
  Example:</p>
  
  <pre><code>flag = False
  if string contains N:
     flag = True
  </code></pre>
  
  <p>So <code>flag = True</code> if string is <code>"CNDDDNTD"</code> and <code>flag = False</code> if string is <code>"CCGGTTT"</code>. I think re.search will work, but not sure of the options to use.</p>