导入错误：没有名为 _sqlite3 的模块

Question

我正在为谷歌的应用引擎写代码，但在本地测试时遇到了以下错误：

-->  --> -->

Traceback (most recent call last):
  File "C:\Program Files\Google\google_appengine\google\appengine\tools\dev_appserver.py", line 3185, in _HandleRequest
    self._Dispatch(dispatcher, self.rfile, outfile, env_dict)
  File "C:\Program Files\Google\google_appengine\google\appengine\tools\dev_appserver.py", line 3128, in _Dispatch
    base_env_dict=env_dict)
  File "C:\Program Files\Google\google_appengine\google\appengine\tools\dev_appserver.py", line 515, in Dispatch
    base_env_dict=base_env_dict)
  File "C:\Program Files\Google\google_appengine\google\appengine\tools\dev_appserver.py", line 2387, in Dispatch
    self._module_dict)
  File "C:\Program Files\Google\google_appengine\google\appengine\tools\dev_appserver.py", line 2297, in ExecuteCGI
    reset_modules = exec_script(handler_path, cgi_path, hook)
  File "C:\Program Files\Google\google_appengine\google\appengine\tools\dev_appserver.py", line 2193, in ExecuteOrImportScript
    exec module_code in script_module.__dict__
  File "C:\Users\Chris Reade\Documents\SI 182\Final\geneticsalesman\Final.py", line 7, in <module>
    from pyevolve import DBAdapters
  File "C:\Program Files\Google\google_appengine\google\appengine\tools\dev_appserver.py", line 1272, in Decorate
    return func(self, *args, **kwargs)
  File "C:\Program Files\Google\google_appengine\google\appengine\tools\dev_appserver.py", line 1922, in load_module
    return self.FindAndLoadModule(submodule, fullname, search_path)
  File "C:\Program Files\Google\google_appengine\google\appengine\tools\dev_appserver.py", line 1272, in Decorate
    return func(self, *args, **kwargs)
  File "C:\Program Files\Google\google_appengine\google\appengine\tools\dev_appserver.py", line 1824, in FindAndLoadModule
    description)
  File "C:\Program Files\Google\google_appengine\google\appengine\tools\dev_appserver.py", line 1272, in Decorate
    return func(self, *args, **kwargs)
  File "C:\Program Files\Google\google_appengine\google\appengine\tools\dev_appserver.py", line 1775, in LoadModuleRestricted
    description)
  File "C:\Users\Chris Reade\Documents\SI 182\Final\geneticsalesman\pyevolve\DBAdapters.py", line 21, in <module>
    import sqlite3
  File "C:\Program Files\Google\google_appengine\google\appengine\tools\dev_appserver.py", line 1272, in Decorate
    return func(self, *args, **kwargs)
  File "C:\Program Files\Google\google_appengine\google\appengine\tools\dev_appserver.py", line 1922, in load_module
    return self.FindAndLoadModule(submodule, fullname, search_path)
  File "C:\Program Files\Google\google_appengine\google\appengine\tools\dev_appserver.py", line 1272, in Decorate
    return func(self, *args, **kwargs)
  File "C:\Program Files\Google\google_appengine\google\appengine\tools\dev_appserver.py", line 1824, in FindAndLoadModule
    description)
  File "C:\Program Files\Google\google_appengine\google\appengine\tools\dev_appserver.py", line 1272, in Decorate
    return func(self, *args, **kwargs)
  File "C:\Program Files\Google\google_appengine\google\appengine\tools\dev_appserver.py", line 1775, in LoadModuleRestricted
    description)
  File "C:\Python26\lib\sqlite3\__init__.py", line 24, in <module>
    from dbapi2 import *
  File "C:\Program Files\Google\google_appengine\google\appengine\tools\dev_appserver.py", line 1272, in Decorate
    return func(self, *args, **kwargs)
  File "C:\Program Files\Google\google_appengine\google\appengine\tools\dev_appserver.py", line 1922, in load_module
    return self.FindAndLoadModule(submodule, fullname, search_path)
  File "C:\Program Files\Google\google_appengine\google\appengine\tools\dev_appserver.py", line 1272, in Decorate
    return func(self, *args, **kwargs)
  File "C:\Program Files\Google\google_appengine\google\appengine\tools\dev_appserver.py", line 1824, in FindAndLoadModule
    description)
  File "C:\Program Files\Google\google_appengine\google\appengine\tools\dev_appserver.py", line 1272, in Decorate
    return func(self, *args, **kwargs)
  File "C:\Program Files\Google\google_appengine\google\appengine\tools\dev_appserver.py", line 1775, in LoadModuleRestricted
    description)
  File "C:\Python26\lib\sqlite3\dbapi2.py", line 27, in <module>
    from _sqlite3 import *
ImportError: No module named _sqlite3

我的Python环境里有一个关于sqlite3的库文件，但我不知道为什么它找不到这个文件。任何帮助都将非常感谢。

Answer 1

当你第一次想在 App Engine 上使用 sqlite3 时，它会试图给你报错。这并不是因为本地的 App Engine 不允许使用 sqlite3 作为替代数据库，而是因为 sqlite3 在生产环境中不被支持。所以，App Engine 是在尽力让你不要使用 sqlite3，以免你在部署应用时搞错了。
如果你想在本地的 App Engine 中使用 sqlite3，你需要把 sqlite3 加入白名单，步骤如下：

首先，去到C:\Program Files (x86)\Google\google_appengine\google\appengine\tools\devappserver2\python\runtime\sandbox.py这个文件夹。
打开这个文件，你会看到一个叫做 _WHITE_LIST_C_MODULES 的常量变量，内容是：

  _WHITE_LIST_C_MODULES = [
        'array',
        '_ast',
        'binascii',
        '_bisect',
         .
         .
         .,
]

然后，按照下面的方式添加 sqlite3：

  _WHITE_LIST_C_MODULES = [
                'array',
                '_ast',
                'binascii',
                '_bisect',
                 .
                 .
                 .,
                _sqlite3,
        ]

希望这对你有帮助。

Answer 2

App Engine SDK会努力让你在导入模块时发现错误，这些错误在真正的App Engine（也就是谷歌的服务器上）会出现。因为SQlite在真正的服务器上是不被支持的，所以SDK给你提示错误，其实就是在友好地告诉你：“你无法把这段代码部署到真正的谷歌App Engine服务器上！”