schema.py 文件源码

def effective_default(self, field):
        """
        Returns a field's effective database default value
        """
        if field.has_default():
            default = field.get_default()
        elif not field.null and field.blank and field.empty_strings_allowed:
            if field.get_internal_type() == "BinaryField":
                default = six.binary_type()
            else:
                default = six.text_type()
        else:
            default = None
        # If it's a callable, call it
        if six.callable(default):
            default = default()
        # Run it through the field's get_db_prep_save method so we can send it
        # to the database.
        default = field.get_db_prep_save(default, self.connection)
        return default