title: How to set NULL for IntegerField instead of setting 0?
body: <p>I'm uploading some data from an excel file using xlrd and turning that data into models (with mainly IntegerField values) in Django. My excel file has a bunch of missing data. Unfortunately, these missing data are converted to the value of 0 in my models, instead of NULL. This means that when my Person model doesn't have an age, that age gets recorded as 0, instead of as NULL.</p>
  
  <p>What's the best way to change this? I've tried doing this:</p>
  
  <pre><code>age = models.IntegerField(blank=True, null=True)
  </code></pre>
  
  <p>But the blank fields still get set to 0 by default.</p>