title: How to make an auto-filled and auto-incrementing field in django admin
body: <p>[<strong>Update:</strong> Changed question title to be more specific]</p>
  
  <p>Sorry if I didn't make the question very well, I can't figure how to do this:</p>
  
  <pre><code>class WhatEver():
      number = model.IntegerField('Just a Field', default=callablefunction)
  ...
  </code></pre>
  
  <p>Where <code>callablefunction</code> does this query:</p>
  
  <pre><code>from myproject.app.models import WhatEver
  
  def callablefunction():
      no = WhatEver.objects.count()
      return no + 1
  </code></pre>
  
  <p>I want to automatically write the next number, and I don't know how to do it.</p>
  
  <p>I have errors from <code>callablefunction</code> stating that it cannot import the model, and I think there must be an easier way to do this. There's no need even to use this, but I can't figure how to do it with the pk number.</p>
  
  <p>I've googled about this and the only thing I found was to use the save() method for auto incrementing the number... but I wanted to show it in the <code>&lt;textfield&gt;</code> before saving...</p>
  
  <p>What would you do?</p>