Restrict django FloatField to 2 decimal places

If you'd like to actually ensure that your model always gets saved with only two decimal places, rather than just changing the presentation of the model in a template, a custom save method on your model will work great. The example model below shows how.

class MyDataModel(models.Model):
    my_float = models.FloatField()

    def save(self, *args, **kwargs):
        self.my_float = round(self.my_float, 2)
        super(MyDataModel, self).save(*args, **kwargs)

Now every time you save your model you will guarantee that the field will only be populated with a float of two decimal places. This can be generalized to rounding to any number of decimal places.

If you are only concerned with how your FloatField appears in forms, you can use the template filter floatformat.

From the Django Docs:

If used with a numeric integer argument, floatformat rounds a number to that many decimal places.

For example, if value = 34.23234, then in your template:

{{ value|floatformat:2 }}  # outputs 34.23

Since Django 1.8+ you can use a custom validator for FloatField/or any ModelFields:

def validate_decimals(value):
    try:
        return round(float(value), 2)
    except:
        raise ValidationError(
            _('%(value)s is not an integer or a float  number'),
            params={'value': value},
        )

...and in your model you can apply it like this:

from django.db import models

class MyModel(models.Model):
    even_field = models.FloatField(validators=[validate_decimals])