AppEngine：模型不是不可变的

Question

我试图将一个模型的实例插入ndb数据库。

它一直给我“模型不是不可变的”错误。

我尝试过不同的模型名称，但仍然是相同的错误。

class User(ndb.Model): 
    username = ndb.StringProperty() 
    email = ndb.StringProperty() 
    lwr_username = ndb.ComputedProperty(lambda self: self.username.lower()) 
    lwr_email = ndb.ComputedProperty(lambda self: self.email.lower()) 

这里是我的插入代码：

entity = User() 
entity.email = "" 
entity.username = "bob" 

logging.info(entity) 

#Commit data asynchronously 
entities = [entity] 
futures = ndb.put_multi_async(entities) 

#Build Response whilst database is committing 
response = { 

} 

#Wait for commits to finish 
ndb.Future.wait_all(entities) 

这是一个完整的堆栈跟踪

Model is not immutable 
Traceback (most recent call last): 
    File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.3/webapp2.py", line 1511, in __call__ 
    rv = self.handle_exception(request, response, e) 
    File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.3/webapp2.py", line 1505, in __call__ 
    rv = self.router.dispatch(request, response) 
    File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.3/webapp2.py", line 1253, in default_dispatcher 
    return route.handler_adapter(request, response) 
    File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.3/webapp2.py", line 1077, in __call__ 
    return handler.dispatch() 
    File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.3/webapp2.py", line 547, in dispatch 
    return self.handle_exception(e, self.app.debug) 
    File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.3/webapp2.py", line 545, in dispatch 
    return method(*args, **kwargs) 
    File "/base/data/home/apps/s~myapp-api/1.377037445874907069/v1/handler/userHandler.py", line 11, in post 
    responseCode, response = UserService.create(locale, json.loads(self.request.body), **kwargs) 
    File "/base/data/home/apps/s~myapp-api/1.377037445874907069/v1/service/userService.py", line 37, in create 
    ndb.Future.wait_all(entities) 
    File "/base/data/home/runtimes/python27/python27_lib/versions/1/google/appengine/ext/ndb/tasklets.py", line 345, in wait_all 
    waiting_on = set(futures) 
    File "/base/data/home/runtimes/python27/python27_lib/versions/1/google/appengine/ext/ndb/model.py", line 3017, in __hash__ 
    raise TypeError('Model is not immutable') 
TypeError: Model is not immutable 

Answer 1

您需要使用futures列表，不entities等待异步过程完成：

ndb.Future.wait_all(futures) 

wait_all()函数将这些函数存储在一个set()对象中，并且设置要求内容可哈希。由于可变对象不能存储在集合或字典中，因此Google工程师在Model.__hash__方法中添加了明确的TypeError，这是您在此处看到的内容。