Method sum

mongoengine/queryset/base.py:1564–1588

Sum over the values of the specified field. :param field: the field to sum over; use dot notation to refer to embedded document fields

(self, field)

        return queryset

    def sum(self, field):
        """Sum over the values of the specified field.

        :param field: the field to sum over; use dot notation to refer to
            embedded document fields
        """
        db_field = self._fields_to_dbfields([field]).pop()
        pipeline = [
            {"$match": self._query},
            {"$group": {"_id": "sum", "total": {"$sum": "$" + db_field}}},
        ]

        # if we're performing a sum over a list field, we sum up all the
        # elements in the list, hence we need to $unwind the arrays first
        ListField = _import_class("ListField")
        field_parts = field.split(".")
        field_instances = self._document._lookup_field(field_parts)
        if isinstance(field_instances[-1], ListField):
            pipeline.insert(1, {"$unwind": "$" + field})

        result = tuple(self._document._get_collection().aggregate(pipeline))

        if result:
            return result[0]["total"]
        return 0

    def average(self, field):
        """Average over the values of the specified field.