How to create a Django FloatField with maximum and minimum limits?

Question

I\'m storing some floating-point data in my Django models, and only a certain range of values are meaningful. Therefore, I\'d like to impose these limits at both the model a

Answer 1

The answers so far describe how to make forms validate. You can also put validators in the model. Use MinValueValidator and MaxValueValidator.

For example:

from django.core.validators import MaxValueValidator, MinValueValidator

...
weight = models.FloatField(
    validators=[MinValueValidator(0.9), MaxValueValidator(58)],
)

I don't think that adds SQL constraints, tho.

Answer 2

If you need constraint on form level you can pass min_value and max_value to form field:

myfloat = forms.FloatField(min_value=0.0, max_value=1.0)

But if you need to move it up to model level you have to extend base models.FloatField class

class MinMaxFloat(models.FloatField):
    def __init__(self, min_value=None, max_value=None, *args, **kwargs):
        self.min_value, self.max_value = min_value, max_value
        super(MinMaxFloat, self).__init__(*args, **kwargs)

    def formfield(self, **kwargs):
        defaults = {'min_value': self.min_value, 'max_value' : self.max_value}
        defaults.update(kwargs)
        return super(MinMaxFloat, self).formfield(**defaults)

Then you can use it in models

class Foo(models.Model):
    myfloat = MinMaxFloat(min_value=0.0, max_value=1.0)