django-expression-fields 0.1.2

django-expression-fields allows typing mathematical expressions into form fields and having only the calculated result stored in the database.

django-expression-fields lets your users type a mathematical expression in a form field. Python does the math and stores the result in the database. For example, suppose you have a model to track Things, like this:

class Thing(models.Model):
    cost = models.DecimalField(
            max_digits=5, decimal_places=2, null=True, blank=True)

Suppose Things come in packs of 12 for $7.99. Your users have to do some math to fill in the cost of a single Thing, $0.67.

But not with an expression field! Create your form like this:

class ThingForm(forms.Form):
        cost = DecimalExpressionField(
                max_digits=5, decimal_places=2, required=False)

Now you user can simply type 7.99/12 in the field and Python will do the math for them!