手动创建对象时未应用Django模型字段的默认值

Question

Say my object has a DecimalField with default set to 20 . When I create an object in python and don't specify a value for that DecimalField , it's None .

How to make sure that default value is applied every time I don't supply a value?

class SomeModel(models.Model):
    """Demonstrate the flaw of the default value."""

    dec_field = models.DecimalField(default=1, blank=True, null=True)


my_model = SomeModel()
my_model.save()  # this is where I expect the dec_field to become Decimal('1.0')
                 # instead it's None

Answer 1

通过使用诸如South之类的迁移工具或删除表并重新同步，确保模型和数据库已同步。

Answer 2

The default should be set with what you have described, would need more info about your example. But if you wanted to override, or set the default manually you could do the following;

DEC_FIELD_DEFAULT = 20
class Example(models.Model):
    dec_field = models.DecimalField(default=DEC_FIELD_DEFAULT)

    def __init__(self, *args, **kwargs):
        super(Example, self).__init__(self, *args, **kwargs)
        self.dec_field = DEC_FIELD_DEFAULT