title: Django Models - Prepare the data for the database
body: <p>I have a form that askes for a phone number.  I need to make sure that only digits [0-9] get saved in the database.  </p>
  
  <p>In the Django <a href="https://docs.djangoproject.com/en/dev/ref/models/instances/" rel="nofollow">documentation </a> it says:</p>
  
  <p>What happens when you save?</p>
  
  <p>3) Prepare the data for the database. Each field is asked to provide its current value in a data type that can be written to the database.</p>
  
  <p>How does this happen?  Or more specifically, how can I make sure this is cleaned?  I know that I can just override the models save method, but it seems like there is a better way and I'm just not sure how to do it.</p>
  
  <p>I guess I could write a custom field for it, but that seems like overkill here.</p>
  
  <p>Also, I realize that I can put the validation on the form, but it really feels like stripping out the characters belongs on the model.</p>