无法在dev_server上运行appengine-admin

Question

我决定尝试这个项目：

http://code.google.com/p/appengine-admin/wiki/QuickStart

为了这个实验，我用了App Engine自带的示例留言簿。导入的代码大概是这样的：

import cgi
import datetime
import wsgiref.handlers

from google.appengine.ext import db
from google.appengine.api import users
from google.appengine.ext import webapp
from google.appengine.ext.webapp.util import run_wsgi_app
from google import appengine_admin

数据库模型和管理界面大概是这样的：

class Greeting(db.Model):

 author = db.UserProperty()
 content = db.StringProperty(multiline=True)
 date = db.DateTimeProperty(auto_now_add=True)

class AdminGreeting(appengine_admin.ModelAdmin):

 model = Greeting
 listFields = ('author','content','date')
 editFields = ('author','content','date')

appengine_admin.register(AdminGreeting)

但是在我尝试运行这个网站时，出现了这个错误：

File "/home/<username>/python/google_appengine/google/appengine/tools/    dev_appserver.py", line 2875, in _HandleRequest
    base_env_dict=env_dict)
  File "/home/<username>/python/google_appengine/google/appengine/tools/dev_appserver.py", line 387, in Dispatch
    base_env_dict=base_env_dict)
  File "/home/<username>/python/google_appengine/google/appengine/tools/dev_appserver.py", line 2162, in Dispatch
    self._module_dict)
  File "/home/<username>/python/google_appengine/google/appengine/tools/dev_appserver.py", line 2080, in ExecuteCGI
    reset_modules = exec_script(handler_path, cgi_path, hook)
  File "/home/<username>/python/google_appengine/google/appengine/tools/dev_appserver.py", line 1976, in ExecuteOrImportScript
    exec module_code in script_module.__dict__
  File "/home/<username>/python/google_appengine/demos/guestbook/guestbook.py", line 37, in <module>
    appengine_admin.register(AdminGreeting)
  File "/home/<username>/python/google_appengine/google/appengine_admin/model_register.py", line 120, in register
    modelAdminInstance = modelAdminClass()
  File "/home/<username>/python/google_appengine/google/appengine_admin/model_register.py", line 64, in __init__
    self._extractProperties(self.listFields, self._listProperties)
  File "/home/<username>/python/google_appengine/google/appengine_admin/model_register.py", line 76, in _extractProperties
    storage.append(PropertyWrapper(getattr(self.model, propertyName), propertyName))
  File "/home/<username>/python/google_appengine/google/appengine_admin/model_register.py", line 17, in __init__
    logging.info("Caching info about property '%s'" % name)
  File "/usr/lib/python2.6/logging/__init__.py", line 1451, in info
    root.info(*((msg,)+args), **kwargs)
  File "/usr/lib/python2.6/logging/__init__.py", line 1030, in info
    self._log(INFO, msg, args, **kwargs)
  File "/usr/lib/python2.6/logging/__init__.py", line 1142, in _log
record = self.makeRecord(self.name, level, fn, lno, msg, args, exc_info, func, extra)
  File "/usr/lib/python2.6/logging/__init__.py", line 1117, in makeRecord
rv = LogRecord(name, level, fn, lno, msg, args, exc_info, func)
  File "/usr/lib/python2.6/logging/__init__.py", line 272, in __init__
from multiprocessing import current_process
  File "/home/<username>/python/google_appengine/google/appengine/tools/dev_appserver.py", line 1089, in decorate
return func(self, *args, **kwargs)
  File "/home/<username>/python/google_appengine/google/appengine/tools/dev_appserver.py", line 1736, in load_module
return self.FindAndLoadModule(submodule, fullname, search_path)
  File "/home/<username>/python/google_appengine/google/appengine/tools/dev_appserver.py", line 1089, in decorate
    return func(self, *args, **kwargs)
  File "/home/<username>/python/google_appengine/google/appengine/tools/dev_appserver.py", line 1638, in FindAndLoadModule
description)
  File "/home/<username>/python/google_appengine/google/appengine/tools/dev_appserver.py", line 1089, in decorate
return func(self, *args, **kwargs)
  File "/home/<username>/python/google_appengine/google/appengine/tools/dev_appserver.py", line 1589, in LoadModuleRestricted
description)
  File "/usr/lib/python2.6/multiprocessing/__init__.py", line 83, in <module>
    import _multiprocessing
ImportError: No module named _multiprocessing
INFO     2009-04-25 23:34:27,628 dev_appserver.py:2934] "GET / HTTP/1.1" 500 -

有人知道可能出了什么问题吗？

Answer 1

正如其他人所说，这个问题出现在Python 2.6版本中。我使用了在App Engine问题追踪器中提到的解决办法：

A quickfix is to create a file in your app's root named `_multiprocessing.py' with 
the contents:

  import multiprocessing

This way it's possible to import the _multiprocessing module.

It worked for me using Python 2.6.2

Cheers,
Kaji

Answer 2

Google App Engine 只支持 Python 2.5，而你现在用的是更新的版本。

从你的文件夹来看，你可能是在用 Linux（或者是 Mac？）。如果你用的是 Ubuntu，可以通过输入“sudo apt-get install python2.5”来安装 Python 2.5（这不会影响你现有的 Python 2.6），然后你可以这样做：

<path-to-gae>/dev_appserver.py ...

这样做

python2.5 <path-to-gae>/dev_appserver.py ...

这样比直接在 Python 2.6 上开发然后再在 Python 2.5 上部署要好得多，这样做以后肯定会遇到麻烦。

Answer 3

你似乎在使用Python 2.6（因为有些信息来自于/usr/lib/python2.6这个文件夹...！），但是Google App Engine需要的是Python 2.5（任何2.5.x的版本都可以），所以你应该安装并使用Python 2.5来运行App Engine的开发工具包。