title: Django RegexField Letters and Numbers only
body: <p>I need a regexfield in a django form to only accept letters and numbers, and nothing else.  I've tried this, but it didn't work:</p>
  
  <pre><code>myfield = forms.RegexField(label=("My Label"), max_length=31, regex=r'[a-zA-Z0-9]',
          error_message = ("This value must contain only letters and numbers."),
  </code></pre>
  
  <p>I am not very good at using regular expressions.  Can you tell me what I am doing wrong here and how to fix it?</p>