g_carbs = DecimalField(max_digits=13, decimal_places = 8, null=True, blank=True)

from django.db.models.fields import DecimalField

class NonscientificDecimalField(DecimalField):
    def format_number(self, value):
        """
        Overrides DecimalField's usual format_number by making sure
        that the result is never in exponential notation for zero.
        """
        if value == 0:
            return "0.00000000"
        else:
            return super(DecimalField, self).format_number(value)

import decimal
from django.db.models.fields import DecimalField

class NonscientificDecimalField(DecimalField):
    def format_number(self, value):
        """
        Overrides DecimalField's usual format_number to remove trailing zeroes.
        """
        if isinstance(value, decimal.Decimal):
            context = decimal.Context(prec=self.max_digits)
            value = value.normalize(context=context)
        return super(DecimalField, self).format_number(value)

class NonscientificDecimalField(DecimalField):
    """ Prevents values from being displayed with E notation, with trailing 0's
        after the decimal place  truncated. (This causes precision to be lost in
        many cases, but is more user friendly and consistent for non-scientist
        users)
    """
    def value_from_object(self, obj):
        def remove_exponent(val):
            """Remove exponent and trailing zeros.
               >>> remove_exponent(Decimal('5E+3'))
               Decimal('5000')
            """
            context = decimal.Context(prec=self.max_digits)
            return val.quantize(decimal.Decimal(1), context=context) if val == val.to_integral() else val.normalize(context)

        val = super(NonscientificDecimalField, self).value_from_object(obj)
        if isinstance(val, decimal.Decimal):
            return remove_exponent(val)