python - 为什么会失败？ (谷歌应用程序引擎数据存储，Python)

Question

  1 from google.appengine.ext import webapp
  2 from google.appengine.ext.webapp.util import run_wsgi_app
  3 from google.appengine.ext import db
  4 
  5 a = db.GqlQuery('SELECT * FROM Store WHERE count = True').count
  6 
  7 print 'Content-Type: text/plain'
  8 print ''
  9 print str(a)+'blah blah'

表“Store”存在。

错误是:

Traceback (most recent call last):
  File "/opt/google-appengine/google/appengine/tools/dev_appserver.py", line 3245, in _HandleRequest
    self._Dispatch(dispatcher, self.rfile, outfile, env_dict)
  File "/opt/google-appengine/google/appengine/tools/dev_appserver.py", line 3186, in _Dispatch
    base_env_dict=env_dict)
  File "/opt/google-appengine/google/appengine/tools/dev_appserver.py", line 531, in Dispatch
    base_env_dict=base_env_dict)
  File "/opt/google-appengine/google/appengine/tools/dev_appserver.py", line 2410, in Dispatch
    self._module_dict)
  File "/opt/google-appengine/google/appengine/tools/dev_appserver.py", line 2320, in ExecuteCGI
    reset_modules = exec_script(handler_path, cgi_path, hook)
  File "/opt/google-appengine/google/appengine/tools/dev_appserver.py", line 2216, in ExecuteOrImportScript
    exec module_code in script_module.__dict__
  File "/home/jck/bitsconv/bitsconv.py", line 5, in <module>
    a = db.GqlQuery('SELECT * FROM Store WHERE count = True').count()
  File "/opt/google-appengine/google/appengine/ext/db/__init__.py", line 2298, in __init__
    model_class = class_for_kind(self._proto_query._entity)
  File "/opt/google-appengine/google/appengine/ext/db/__init__.py", line 266, in class_for_kind
    raise KindError('No implementation for kind \'%s\'' % kind)
KindError: No implementation for kind 'Store'

Answer 1

您需要为“Store”定义一个模型。即使您已成功将数据作为存储行获取到数据存储中，当模型类不存在时，此操作也会失败。

我通过在工作应用程序中重命名我的模型类之一来验证这一点，该应用程序存储了该类型对象的数据。它引发了相同的异常，所以我猜这也是您问题的原因。将其添加到应用程序中的某个位置，然后查看它是否更改了错误:

class Store(db.Model):
    pass

此外，这不会导致错误，但 count 实际上是一种方法。你应该使用这个:

a = db.GqlQuery('SELECT * FROM Store WHERE count = True').count()