Method aggregate

pymongo/synchronous/collection.py:2944–3046

Perform an aggregation using the aggregation framework on this collection. The :meth:`aggregate` method obeys the :attr:`read_preference` of this :class:`Collection`, except when ``$out`` or ``$merge`` are used on MongoDB <5.0, in which case :attr:`~pymongo.r

(
        self,
        pipeline: _Pipeline,
        session: Optional[ClientSession] = None,
        let: Optional[Mapping[str, Any]] = None,
        comment: Optional[Any] = None,
        **kwargs: Any,
    )

        )

    def aggregate(
        self,
        pipeline: _Pipeline,
        session: Optional[ClientSession] = None,
        let: Optional[Mapping[str, Any]] = None,
        comment: Optional[Any] = None,
        **kwargs: Any,
    ) -> CommandCursor[_DocumentType]:
        """Perform an aggregation using the aggregation framework on this
        collection.

        The :meth:`aggregate` method obeys the :attr:`read_preference` of this
        :class:`Collection`, except when ``$out`` or ``$merge`` are used on
        MongoDB <5.0, in which case
        :attr:`~pymongo.read_preferences.ReadPreference.PRIMARY` is used.

        .. note:: This method does not support the 'explain' option. Please
           use `PyMongoExplain <https://pypi.org/project/pymongoexplain/>`_
           instead. An example is included in the `aggregation example <https://www.mongodb.com/docs/languages/python/pymongo-driver/current/aggregation/#aggregation-example>`_
           documentation.

        .. note:: The :attr:`~pymongo.collection.Collection.write_concern` of
           this collection is automatically applied to this operation.

        Cursors are closed automatically when they are exhausted (the last batch of data is retrieved from the database).
        If a cursor is not exhausted, it will be closed automatically upon garbage collection, which leaves resources open but unused for a potentially long period of time.
        To avoid this, best practice is to call :meth:`Cursor.close` when the cursor is no longer needed,
        or use the cursor in a with statement::

            with collection.aggregate() as cursor:
                for operation in cursor:
                    print(operation)

        :param pipeline: a list of aggregation pipeline stages
        :param session: a
            :class:`~pymongo.client_session.ClientSession`.
        :param let: A dict of parameter names and values. Values must be
            constant or closed expressions that do not reference document
            fields. Parameters can then be accessed as variables in an
            aggregate expression context (e.g. ``"$$var"``). This option is
            only supported on MongoDB >= 5.0.
        :param comment: A user-provided comment to attach to this
            command.
        :param kwargs: extra `aggregate command`_ parameters.

        All optional `aggregate command`_ parameters should be passed as
        keyword arguments to this method. Valid options include, but are not
        limited to:

          - `allowDiskUse` (bool): Enables writing to temporary files. When set
            to True, aggregation stages can write data to the _tmp subdirectory
            of the --dbpath directory. The default is False.
          - `maxTimeMS` (int): The maximum amount of time to allow the operation
            to run in milliseconds.
          - `batchSize` (int): The maximum number of documents to return per
            batch. Ignored if the connected mongod or mongos does not support
            returning aggregate results using a cursor.
          - `collation` (optional): An instance of