import decimal from django.db import models class Cash(decimal.Decimal): currency = 'USD' def __str__(self): s = super().__str__(self) return '%s %s' % (s, self.currency) class CashField(models.DecimalField): def __init__(self, **kwargs): kwargs['max_digits'] = 20 kwargs['decimal_places'] = 2 super().__init__(**kwargs) def from_db_value(self, value, expression, connection, context): cash = Cash(value) cash.vendor = connection.vendor return cash class CashModel(models.Model): cash = CashField() def __str__(self): return str(self.cash)