如何使用 python win32com 或 comtypes 中的 COM 访问 IRTDServer？

环境

Windows 10 + python 3.6.3 64 位（也尝试过 32 位）。我是一名 Python 开发人员，（几乎）第一次尝试使用 COM，但遇到了这个巨大的障碍。

Problem

当我尝试使用在 dll 中实现的 IRTDServer（不是我写的）时，我遇到了各种错误，通过win32com or comtypes. Using win32com事实证明更加困难。我为下面的两个库提供了一个示例单元测试。

从 Excel 2016 访问服务器按预期工作；这将返回预期值：

=RTD("foo.bar", , "STAT1", "METRIC1")

使用 win32com 库的代码

这是一个简单的测试用例，应该连接到服务器，但没有。 （这只是一个版本，因为我已经多次更改它来尝试调试问题。）

from unittest import TestCase

class COMtest(TestCase):
    def test_win32com(self):
        import win32com.client
        from win32com.server.util import wrap

        class RTDclient:
            # are these only required when implementing the server?
            _com_interfaces_ = ["IRTDUpdateEvent"]
            _public_methods_ = ["Disconnect", "UpdateNotify"]
            _public_attrs_ = ["HeartbeatInterval"]

            def __init__(self, *args, **kwargs):
                self._comObj = win32com.client.Dispatch(*args, **kwargs)
            def connect(self):
                self._rtd = win32com.client.CastTo(self._comObj, 'IRtdServer')
                result = self._rtd.ServerStart(wrap(self))
                assert result > 0

            def UpdateNotify(self):
                print("UpdateNotify() callback")
            def Disconnect(self):
                print("Disconnect() called")
            HeartbeatInterval = -1

_rtd = RTDclient("foo.bar")
_rtd.connect()

Result:

Traceback (most recent call last):
  File "env\lib\site-packages\win32com\client\gencache.py", line 532, in EnsureDispatch
    ti = disp._oleobj_.GetTypeInfo()
pywintypes.com_error: (-2147467263, 'Not implemented', None, None)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "test\test.py", line 23, in test_win32com
    _rtd.connect()
  File "test\test.py", line 16, in connect
    self._rtd = win32com.client.CastTo(dispatch, 'IRtdServer')
  File "env\lib\site-packages\win32com\client\__init__.py", line 134, in CastTo
    ob = gencache.EnsureDispatch(ob)
  File "env\lib\site-packages\win32com\client\gencache.py", line 543, in EnsureDispatch
    raise TypeError("This COM object can not automate the makepy process - please run makepy manually for this object")
TypeError: This COM object can not automate the makepy process - please run makepy manually for this object

按照这些指示，我运行了makepy脚本成功：

> env\Scripts\python.exe env\lib\site-packages\win32com\client\makepy.py "foo.bar"
Generating to C:\Users\user1\AppData\Local\Temp\gen_py\3.5\longuuid1x0x1x0.py
Building definitions from type library...
Generating...
Importing module

（出于隐私考虑，我替换了 stackoverflow 上的 UUID。此 UUID 与“foo.bar”的 typelib UUID 相同。）

生成的文件包含两者的各种函数和类型定义IRtdServer and IRTDUpdateEvent。但在这个文件中，两个接口都是win32com.client.DispatchBaseClass，而根据 OleViewDotNet，它们应该是IUnknown?

然而，当我尝试再次运行单元测试时，我收到了与之前完全相同的错误。好像查找机制没有找到生成的模块？

Also, GetTypeInfo返回Not implemented让我感到震惊。据我了解，win32com 使用该方法（部分IDispatchCOM 接口）来确定其他接口中所有其他函数的参数和返回类型，包括IRtdServer。如果不实现，将无法正确确定类型。然而，生成的文件似乎包含这些信息，这也令人困惑。

使用 comtypes 库的代码

from unittest import TestCase

class COMtest(TestCase):
    def test_comtypes(self):
        import comtypes.client

        class RTDclient:
            # are these for win32com only?
            _com_interfaces_ = ["IRTDUpdateEvent"]
            _public_methods_ = ["Disconnect", "UpdateNotify"]
            _public_attrs_ = ["HeartbeatInterval"]

            def __init__(self, clsid):
                self._comObj = comtypes.client.CreateObject(clsid)
            def connect(self):
                self._rtd = self._comObj.IRtdServer()
                result = self._rtd.ServerStart(self)
                assert result > 0

            def UpdateNotify(self):
                print("UpdateNotify() callback")
            def Disconnect(self):
                print("Disconnect() called")
            HeartbeatInterval = -1

_rtd = RTDclient("foo.bar")
_rtd.connect()

Result:

  File "test\test.py", line 27, in test_comtypes
    _rtd.connect()
  File "test\test.py", line 16, in connect
    self._rtd = self._comObj.IRTDServer()
  File "env\lib\site-packages\comtypes\client\dynamic.py", line 110, in __getattr__
    dispid = self._comobj.GetIDsOfNames(name)[0]
  File "env\lib\site-packages\comtypes\automation.py", line 708, in GetIDsOfNames
    self.__com_GetIDsOfNames(riid_null, arr, len(names), lcid, ids)
_ctypes.COMError: (-2147352570, 'Unknown name.', (None, None, None, 0, None))

我尝试过的其他一些解决方案

（基于谷歌搜索和下面评论中的答案）

• （重新）注册 DLL
• 注册了32位版本的DLL并尝试了python 32位
• 设置兼容模式python.exe至 Windows XP SP3

• 尝试不实例化 IRtdServer，即替换这两行：

  self._rtd = self._comObj.IRtdServer()
  result = self._rtd.ServerStart(self)
  

  with:

  result = self._comObj.ServerStart(self)
  

  这次的错误是：

  TypeError: 'NoneType' object is not callable
  

  这似乎表明ServerStart函数存在，但未定义？ （看起来真的很奇怪。这个谜一定还有更多。）

• 尝试通过interface="IRtdServer"参数为CreateObject:

  def __init__(self, clsid):
      self._comObj = comtypes.client.CreateObject(clsid, interface="IRtdServer")
  def connect(self):
      result = self._comObj.ServerStart(self)
      ...
  

  收到的错误是：

    File "test\test.py", line 13, in __init__
      self._comObj = comtypes.client.CreateObject(clsid, interface="IRtdServer")
    File "env\lib\site-packages\comtypes\client\__init__.py", line 238, in CreateObject
      obj = comtypes.CoCreateInstance(clsid, clsctx=clsctx, interface=interface)
    File "env\lib\site-packages\comtypes\__init__.py", line 1223, in CoCreateInstance
      p = POINTER(interface)()
  TypeError: Cannot create instance: has no _type_
  

  跟踪代码在comtypes库，这似乎表明接口参数需要一个接口类，而不是一个字符串。我发现了定义的各种接口comtypes图书馆：IDispatch, IPersist, IServiceProvider。都是以下类的子类IUnknown。根据 OleViewDotNet 的说法，IRtdServer也是一个子类IUnknown。这让我相信我需要在 python 中类似地编写一个 IRtdServer 类才能使用该接口，但我不知道该怎么做。

• 我注意到dynamic的参数CreateObject。该代码表明这是互斥的interface参数，所以我尝试了：

  def __init__(self, clsid):
      self._comObj = comtypes.client.CreateObject(clsid, dynamic=True)
  def connect(self):
      self._rtd = self._comObj.IRtdServer()
      result = self._rtd.ServerStart(self)
  

  但错误与我原来的错误相同：IRtdServer has _ctypes.COMError: (-2147352570, 'Unknown name.', (None, None, None, 0, None))

任何帮助或线索将不胜感激。先感谢您。

（不太知道我在做什么，）我尝试使用 OleViewDotNet 来查看 DLL：

我遇到了同样的问题。

我还尝试使用 win32com 让 excel 运行，说实话，这有点不稳定......我什至不能碰我的 Excel。

因此我花了一些时间研究这个问题。问题出在 CastTo 上。认为您（和我）加载的 COM 对象不包含足够的信息来进行转换（某些方法如 GetTypeInfo 未实现等...）

因此，我创建了一个包装器，使这些 COM 对象的方法可调用……这并不明显。这似乎对我有用。

客户端代码是从一个名为 Pyrtd 的项目修改而来的，该项目由于各种原因而无法工作（认为是由于 RTD 模型的更改......RefreshData 的返回现在完全不同）。

import functools

import pythoncom
import win32com.client
from win32com import universal
from win32com.client import gencache
from win32com.server.util import wrap


EXCEL_TLB_GUID = '{00020813-0000-0000-C000-000000000046}'
EXCEL_TLB_LCID = 0
EXCEL_TLB_MAJOR = 1
EXCEL_TLB_MINOR = 4

gencache.EnsureModule(EXCEL_TLB_GUID, EXCEL_TLB_LCID, EXCEL_TLB_MAJOR, EXCEL_TLB_MINOR)

universal.RegisterInterfaces(EXCEL_TLB_GUID,
                             EXCEL_TLB_LCID, EXCEL_TLB_MAJOR, EXCEL_TLB_MINOR,
                             ['IRtdServer', 'IRTDUpdateEvent'])


# noinspection PyProtectedMember
class ObjectWrapperCOM:
    """
    This object can act as a wrapper for an object dispatched using win32com.client.Dispatch
    Sometimes the object written by 3rd party is not well constructed that win32com will not be able to obtain
    type information etc in order to cast the object to a certain interface. win32com.client.CastTo will fail.

    This wrapper class will enable the object to call its methods in this case, even if we do not know what exactly
    the wrapped object is.
    """
    LCID = 0x0

    def __init__(self, obj):
        self._impl = obj  # type: win32com.client.CDispatch

    def __getattr__(self, item):
        flags, dispid = self._impl._find_dispatch_type_(item)
        if dispid is None:
            raise AttributeError("{} is not a valid property or method for this object.".format(item))
        return functools.partial(self._impl._oleobj_.Invoke, dispid, self.LCID, flags, True)


# noinspection PyPep8Naming
class RTDUpdateEvent:
    """
    Implements interface IRTDUpdateEvent from COM imports
    """
    _com_interfaces_ = ['IRTDUpdateEvent']
    _public_methods_ = ['Disconnect', 'UpdateNotify']
    _public_attrs_ = ['HeartbeatInterval']

    # Implementation of IRTDUpdateEvent.
    HeartbeatInterval = -1

    def __init__(self, event_driven=True):
        self.ready = False
        self._event_driven = event_driven

    def UpdateNotify(self):
        if self._event_driven:
            self.ready = True

    def Disconnect(self):
        pass


class RTDClient:
    """
    Implements a Real-Time-Data (RTD) client for accessing COM data sources that provide an IRtdServer interface.
    """

    MAX_REGISTERED_TOPICS = 1024

    def __init__(self, class_id):
        """
        :param classid: can either be class ID or program ID
        """
        self._class_id = class_id
        self._rtd = None
        self._update_event = None

        self._topic_to_id = {}
        self._id_to_topic = {}
        self._topic_values = {}
        self._last_topic_id = 0

    def connect(self, event_driven=True):
        """
        Connects to the RTD server.

        Set event_driven to false if you to disable update notifications.
        In this case you'll need to call refresh_data manually.
        """

        dispatch = win32com.client.Dispatch(self._class_id)
        self._update_event = RTDUpdateEvent(event_driven)
        try:
            self._rtd = win32com.client.CastTo(dispatch, 'IRtdServer')
        except TypeError:
            # Automated makepy failed...no detailed construction available for the class
            self._rtd = ObjectWrapperCOM(dispatch)

        self._rtd.ServerStart(wrap(self._update_event))

    def update(self):
        """
        Check if there is data waiting and call RefreshData if necessary. Returns True if new data has been received.
        Note that you should call this following a call to pythoncom.PumpWaitingMessages(). If you neglect to
        pump the message loop you'll never receive UpdateNotify callbacks.
        """
        # noinspection PyUnresolvedReferences
        pythoncom.PumpWaitingMessages()
        if self._update_event.ready:
            self._update_event.ready = False
            self.refresh_data()
            return True
        else:
            return False

    def refresh_data(self):
        """
        Grabs new data from the RTD server.
        """

        (ids, values) = self._rtd.RefreshData(self.MAX_REGISTERED_TOPICS)
        for id_, value in zip(ids, values):
            if id_ is None and value is None:
                # This is probably the end of message
                continue
            assert id_ in self._id_to_topic, "Topic ID {} is not registered.".format(id_)
            topic = self._id_to_topic[id_]
            self._topic_values[topic] = value

    def get(self, topic: tuple):
        """
        Gets the value of a registered topic. Returns None if no value is available. Throws an exception if
        the topic isn't registered.
        """
        assert topic in self._topic_to_id, 'Topic %s not registered.' % (topic,)
        return self._topic_values.get(topic)

    def register_topic(self, topic: tuple):
        """
        Registers a topic with the RTD server. The topic's value will be updated in subsequent data refreshes.
        """
        if topic not in self._topic_to_id:
            id_ = self._last_topic_id
            self._last_topic_id += 1

            self._topic_to_id[topic] = id_
            self._id_to_topic[id_] = topic

            self._rtd.ConnectData(id_, topic, True)

    def unregister_topic(self, topic: tuple):
        """
        Un-register topic so that it will not get updated.
        :param topic:
        :return:
        """
        assert topic in self._topic_to_id, 'Topic %s not registered.' % (topic,)
        self._rtd.DisconnectData(self._topic_to_id[topic])

    def disconnect(self):
        """
        Closes RTD server connection.
        :return:
        """
        self._rtd.ServerTerminate()