TypeError: 'Collection' object is not callable. If you meant to call the 'update' method on a 'Collection' object it is failing because no such method exists.

Flask ：             2.0.3

Flask-Session：      0.4.0

pymongo ：           4.0.1

session:错误信息

TypeError: 'Collection' object is not callable. If you meant to call the 'update' method on a 'Collection' object it is failing because no such method exists.

报错原因：

　　pymongo4.0.0.1 发生了很大的改变，但是flask-session 依然使用老版的pymong，导致内部函数已经被删除修改，所以需要手动修改

将 venv/Lib/site-packages/flask_session/sessions.py 内的 MongoDBSessionInterface 替换 下面代码的代码：

　　

class MongoDBSessionInterface(SessionInterface):
    """A Session interface that uses mongodb as backend.

    .. versionadded:: 0.2
        The `use_signer` parameter was added.

    :param client: A ``pymongo.MongoClient`` instance.
    :param db: The database you want to use.
    :param collection: The collection you want to use.
    :param key_prefix: A prefix that is added to all MongoDB store keys.
    :param use_signer: Whether to sign the session id cookie or not.
    :param permanent: Whether to use permanent session or not.
    """

    serializer = pickle
    session_class = MongoDBSession

    def __init__(self, client, db, collection, key_prefix, use_signer=False,
                 permanent=True):
        if client is None:
            from pymongo import MongoClient
            client = MongoClient()
        self.client = client
        self.store = client[db][collection]
        self.key_prefix = key_prefix
        self.use_signer = use_signer
        self.permanent = permanent
        self.has_same_site_capability = hasattr(self, "get_cookie_samesite")

    def open_session(self, app, request):
        sid = request.cookies.get(app.session_cookie_name)
        if not sid:
            sid = self._generate_sid()
            return self.session_class(sid=sid, permanent=self.permanent)
        if self.use_signer:
            signer = self._get_signer(app)
            if signer is None:
                return None
            try:
                sid_as_bytes = signer.unsign(sid)
                sid = sid_as_bytes.decode()
            except BadSignature:
                sid = self._generate_sid()
                return self.session_class(sid=sid, permanent=self.permanent)

        store_id = self.key_prefix + sid
        document = self.store.find_one({'id': store_id})
        if document and document.get('expiration') <= datetime.utcnow():
            # Delete expired session
            self.store.delete_many({'id': store_id})
            document = None
        if document is not None:
            try:
                val = document['val']
                data = self.serializer.loads(want_bytes(val))
                return self.session_class(data, sid=sid)
            except:
                return self.session_class(sid=sid, permanent=self.permanent)
        return self.session_class(sid=sid, permanent=self.permanent)

    def save_session(self, app, session, response):
        domain = self.get_cookie_domain(app)
        path = self.get_cookie_path(app)
        store_id = self.key_prefix + session.sid
        if not session:
            if session.modified:
                self.store.delete_many({'id': store_id})
                response.delete_cookie(app.session_cookie_name,
                                       domain=domain, path=path)
            return

        conditional_cookie_kwargs = {}
        httponly = self.get_cookie_httponly(app)
        secure = self.get_cookie_secure(app)
        if self.has_same_site_capability:
            conditional_cookie_kwargs["samesite"] = self.get_cookie_samesite(app)
        expires = self.get_expiration_time(app, session)
        val = self.serializer.dumps(dict(session))

        whe     = {'id': store_id}
        data_   = {'id': store_id,'val': val,'expiration': expires }
        if  self.store.count_documents(whe)>0:
            self.store.update_many(whe, {"$set":data_})
        else:
             self.store.insert_one(data_)

        if self.use_signer:
            session_id = self._get_signer(app).sign(want_bytes(session.sid))
        else:
            session_id = session.sid
        response.set_cookie(app.session_cookie_name, session_id,
                            expires=expires, httponly=httponly,
                            domain=domain, path=path, secure=secure,
                            **conditional_cookie_kwargs)