Formatting the stored data into less decimal points

[apaxson]

I'm just now starting out how to modify/create custom widgets. It will take awhile. Right now, my work is trying to learn how to format the scientific notation being stored in the DB from a "converted" unit into less decimal points.

If I put in Liters, and the display is in Gallons, I would get a number to the 10th decimal. Looking to rounding the number for display.

[apaxson]

Here's what I used in my models.py:

class PrecisionQuantityField(QuantityField):
    def __init__(self, base_units, *args, unit_choices, precision='.2f', **kwargs):
        super().__init__(base_units, *args, unit_choices, **kwargs)
        self.ureg.default_format = precision

    def deconstruct(self):
        name, path, args, kwargs = super().deconstruct()
        kwargs['precision'] = self.ureg.default_format
        del kwargs['verbose_name'] #FIXME - Getting duplicate value from super().  Forcing removal
        return name, path, args, kwargs


class MyModelExample(models.Model):
    amount_weight = PrecisionQuantityField('kilograms', null=True, blank=True, unit_choices=['lb', 'gram', 'oz', 'milligram', 'kilogram'], precision='.5f')
    amount_volume = PrecisionQuantityField('liters', null=True, blank=True, unit_choices=['floz', 'ml', 'gallon', 'liter'])

This will allow you to set a default to a precision of 2 decimals places. But, you can set it to a greater precision used the named argument 'precision'.

You will need to do the same thing for QuantityFormField, if you want the same in a form.