Python 导入web2py'；s DAL将与应用程序引擎上的Google Cloud SQL一起使用

我想在AppEngine上构建一个应用程序，它使用云SQL作为后端数据库，而不是AppEngine自己的数据存储设施（不支持常见的SQL操作，如JOIN）

云SQL有一个DB-API，因此我正在寻找一个轻量级数据抽象层（DAL）来帮助轻松地操作云数据库。一项小小的研究表明web2py有一个非常整洁的DAL，它与云SQL兼容

因为我实际上并不需要整个完整的web2py框架，所以我将dal.py文件从/glion文件夹复制到了一个简单测试应用程序的主目录中，并在我的应用程序中包含了这一行：

from dal import DAL, Field

db=DAL('google:sql://myproject:myinstance/mydatabase')

但是，这在我部署应用程序并尝试运行它之后生成了一个错误

Traceback (most recent call last):
  File "/base/python_runtime/python_lib/versions/1/google/appengine/ext/webapp/_webapp25.py", line 701, in __call__
    handler.get(*groups)
  File "/base/data/home/apps/jarod-helloworld/2.357593994022416181/helloworld2.py", line 13, in get
    db=DAL('google:sql://serangoon213home:rainman001/guestbook')
  File "/base/data/home/apps/jarod-helloworld/2.357593994022416181/dal.py", line 5969, in __init__
    raise RuntimeError, "Failure to connect, tried %d times:\n%s" % (attempts, tb)
RuntimeError: Failure to connect, tried 5 times:
Traceback (most recent call last):
  File "/base/data/home/apps/jarod-helloworld/2.357593994022416181/dal.py", line 5956, in __init__
    self._adapter = ADAPTERS[self._dbname](*args)
  File "/base/data/home/apps/jarod-helloworld/2.357593994022416181/dal.py", line 3310, in __init__
    self.folder = folder or '$HOME/'+thread.folder.split('/applications/',1)[1]
  File "/base/python_runtime/python_dist/lib/python2.5/_threading_local.py", line 199, in __getattribute__
    return object.__getattribute__(self, name)
AttributeError: 'local' object has no attribute 'folder'

似乎是由于语句分配的“folder”属性出错所致

self.folder = folder or '$HOME/'+thread.folder.split('/applications/',1)[1]

---

是否有人知道此属性的作用以及如何解决此问题？

文件夹是DAL构造函数中的一个参数。它指向存储DBs（sqlite）的文件夹。因此，我认为这不是你的问题所在。我会再次检查连接字符串

从web2py文档：

The DAL can be used from any Python program simply by doing this:

from gluon import DAL, Field
db = DAL('sqlite://storage.sqlite',folder='path/to/app/databases')
i.e. import the DAL, Field, connect and specify the folder which contains the .table files (the app/databases folder).

To access the data and its attributes we still have to define all the tables we are going to access with db.define_tables(...).

If we just need access to the data but not to the web2py table attributes, we get away without re-defining the tables but simply asking web2py to read the necessary info from the metadata in the .table files:

from gluon import DAL, Field
db = DAL('sqlite://storage.sqlite',folder='path/to/app/databases',
         auto_import=True))
This allows us to access any db.table without need to re-define it.