410 lines
16 KiB
Python
410 lines
16 KiB
Python
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"""Excel IRTDServer implementation.
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This module is a functional example of how to implement the IRTDServer interface
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in python, using the pywin32 extensions. Further details, about this interface
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and it can be found at:
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http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnexcl2k2/html/odc_xlrtdfaq.asp
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"""
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# Copyright (c) 2003-2004 by Chris Nilsson <chris@slort.org>
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#
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# By obtaining, using, and/or copying this software and/or its
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# associated documentation, you agree that you have read, understood,
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# and will comply with the following terms and conditions:
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#
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# Permission to use, copy, modify, and distribute this software and
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# its associated documentation for any purpose and without fee is
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# hereby granted, provided that the above copyright notice appears in
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# all copies, and that both that copyright notice and this permission
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# notice appear in supporting documentation, and that the name of
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# Christopher Nilsson (the author) not be used in advertising or publicity
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# pertaining to distribution of the software without specific, written
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# prior permission.
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#
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# THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD
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# TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANT-
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# ABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR
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# BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY
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# DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
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# WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
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# ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
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# OF THIS SOFTWARE.
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import pythoncom
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import win32com.client
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from win32com import universal
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from win32com.client import gencache
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from win32com.server.exception import COMException
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import threading
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import datetime # For the example classes...
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# Typelib info for version 10 - aka Excel XP.
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# This is the minimum version of excel that we can work with as this is when
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# Microsoft introduced these interfaces.
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EXCEL_TLB_GUID = '{00020813-0000-0000-C000-000000000046}'
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EXCEL_TLB_LCID = 0
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EXCEL_TLB_MAJOR = 1
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EXCEL_TLB_MINOR = 4
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# Import the excel typelib to make sure we've got early-binding going on.
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# The "ByRef" parameters we use later won't work without this.
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gencache.EnsureModule(EXCEL_TLB_GUID, EXCEL_TLB_LCID, \
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EXCEL_TLB_MAJOR, EXCEL_TLB_MINOR)
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# Tell pywin to import these extra interfaces.
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# --
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# QUESTION: Why? The interfaces seem to descend from IDispatch, so
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# I'd have thought, for example, calling callback.UpdateNotify() (on the
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# IRTDUpdateEvent callback excel gives us) would work without molestation.
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# But the callback needs to be cast to a "real" IRTDUpdateEvent type. Hmm...
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# This is where my small knowledge of the pywin framework / COM gets hazy.
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# --
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# Again, we feed in the Excel typelib as the source of these interfaces.
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universal.RegisterInterfaces(EXCEL_TLB_GUID,
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EXCEL_TLB_LCID, EXCEL_TLB_MAJOR, EXCEL_TLB_MINOR,
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['IRtdServer','IRTDUpdateEvent'])
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class ExcelRTDServer(object):
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"""Base RTDServer class.
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Provides most of the features needed to implement the IRtdServer interface.
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Manages topic adding, removal, and packing up the values for excel.
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Shouldn't be instanciated directly.
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Instead, descendant classes should override the CreateTopic() method.
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Topic objects only need to provide a GetValue() function to play nice here.
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The values given need to be atomic (eg. string, int, float... etc).
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Also note: nothing has been done within this class to ensure that we get
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time to check our topics for updates. I've left that up to the subclass
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since the ways, and needs, of refreshing your topics will vary greatly. For
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example, the sample implementation uses a timer thread to wake itself up.
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Whichever way you choose to do it, your class needs to be able to wake up
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occaisionally, since excel will never call your class without being asked to
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first.
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Excel will communicate with our object in this order:
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1. Excel instanciates our object and calls ServerStart, providing us with
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an IRTDUpdateEvent callback object.
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2. Excel calls ConnectData when it wants to subscribe to a new "topic".
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3. When we have new data to provide, we call the UpdateNotify method of the
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callback object we were given.
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4. Excel calls our RefreshData method, and receives a 2d SafeArray (row-major)
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containing the Topic ids in the 1st dim, and the topic values in the
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2nd dim.
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5. When not needed anymore, Excel will call our DisconnectData to
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unsubscribe from a topic.
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6. When there are no more topics left, Excel will call our ServerTerminate
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method to kill us.
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Throughout, at undetermined periods, Excel will call our Heartbeat
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method to see if we're still alive. It must return a non-zero value, or
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we'll be killed.
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NOTE: By default, excel will at most call RefreshData once every 2 seconds.
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This is a setting that needs to be changed excel-side. To change this,
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you can set the throttle interval like this in the excel VBA object model:
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Application.RTD.ThrottleInterval = 1000 ' milliseconds
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"""
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_com_interfaces_ = ['IRtdServer']
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_public_methods_ = ['ConnectData','DisconnectData','Heartbeat',
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'RefreshData','ServerStart','ServerTerminate']
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_reg_clsctx_ = pythoncom.CLSCTX_INPROC_SERVER
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#_reg_clsid_ = "# subclass must provide this class attribute"
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#_reg_desc_ = "# subclass should provide this description"
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#_reg_progid_ = "# subclass must provide this class attribute"
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ALIVE = 1
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NOT_ALIVE = 0
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def __init__(self):
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"""Constructor"""
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super(ExcelRTDServer, self).__init__()
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self.IsAlive = self.ALIVE
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self.__callback = None
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self.topics = {}
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def SignalExcel(self):
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"""Use the callback we were given to tell excel new data is available."""
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if self.__callback is None:
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raise COMException(desc="Callback excel provided is Null")
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self.__callback.UpdateNotify()
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def ConnectData(self, TopicID, Strings, GetNewValues):
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"""Creates a new topic out of the Strings excel gives us."""
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try:
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self.topics[TopicID] = self.CreateTopic(Strings)
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except Exception as why:
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raise COMException(desc=str(why))
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GetNewValues = True
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result = self.topics[TopicID]
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if result is None:
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result = "# %s: Waiting for update" % self.__class__.__name__
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else:
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result = result.GetValue()
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# fire out internal event...
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self.OnConnectData(TopicID)
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# GetNewValues as per interface is ByRef, so we need to pass it back too.
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return result, GetNewValues
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def DisconnectData(self, TopicID):
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"""Deletes the given topic."""
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self.OnDisconnectData(TopicID)
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if TopicID in self.topics:
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self.topics[TopicID] = None
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del self.topics[TopicID]
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def Heartbeat(self):
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"""Called by excel to see if we're still here."""
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return self.IsAlive
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def RefreshData(self, TopicCount):
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"""Packs up the topic values. Called by excel when it's ready for an update.
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Needs to:
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* Return the current number of topics, via the "ByRef" TopicCount
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* Return a 2d SafeArray of the topic data.
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- 1st dim: topic numbers
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- 2nd dim: topic values
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We could do some caching, instead of repacking everytime...
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But this works for demonstration purposes."""
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TopicCount = len(self.topics)
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self.OnRefreshData()
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# Grow the lists, so we don't need a heap of calls to append()
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results = [[None] * TopicCount, [None] * TopicCount]
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# Excel expects a 2-dimensional array. The first dim contains the
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# topic numbers, and the second contains the values for the topics.
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# In true VBA style (yuck), we need to pack the array in row-major format,
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# which looks like:
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# ( (topic_num1, topic_num2, ..., topic_numN), \
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# (topic_val1, topic_val2, ..., topic_valN) )
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for idx, topicdata in enumerate(self.topics.items()):
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topicNum, topic = topicdata
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results[0][idx] = topicNum
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results[1][idx] = topic.GetValue()
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# TopicCount is meant to be passed to us ByRef, so return it as well, as per
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# the way pywin32 handles ByRef arguments.
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return tuple(results), TopicCount
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def ServerStart(self, CallbackObject):
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"""Excel has just created us... We take its callback for later, and set up shop."""
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self.IsAlive = self.ALIVE
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if CallbackObject is None:
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raise COMException(desc='Excel did not provide a callback')
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# Need to "cast" the raw PyIDispatch object to the IRTDUpdateEvent interface
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IRTDUpdateEventKlass = win32com.client.CLSIDToClass.GetClass('{A43788C1-D91B-11D3-8F39-00C04F3651B8}')
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self.__callback = IRTDUpdateEventKlass(CallbackObject)
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self.OnServerStart()
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return self.IsAlive
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def ServerTerminate(self):
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"""Called when excel no longer wants us."""
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self.IsAlive = self.NOT_ALIVE # On next heartbeat, excel will free us
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self.OnServerTerminate()
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def CreateTopic(self, TopicStrings=None):
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"""Topic factory method. Subclass must override.
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Topic objects need to provide:
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* GetValue() method which returns an atomic value.
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Will raise NotImplemented if not overridden.
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"""
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raise NotImplemented('Subclass must implement')
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# Overridable class events...
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def OnConnectData(self, TopicID):
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"""Called when a new topic has been created, at excel's request."""
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pass
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def OnDisconnectData(self, TopicID):
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"""Called when a topic is about to be deleted, at excel's request."""
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pass
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def OnRefreshData(self):
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"""Called when excel has requested all current topic data."""
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pass
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def OnServerStart(self):
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"""Called when excel has instanciated us."""
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pass
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def OnServerTerminate(self):
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"""Called when excel is about to destroy us."""
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pass
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class RTDTopic(object):
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"""Base RTD Topic.
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Only method required by our RTDServer implementation is GetValue().
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The others are more for convenience."""
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def __init__(self, TopicStrings):
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super(RTDTopic, self).__init__()
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self.TopicStrings = TopicStrings
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self.__currentValue = None
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self.__dirty = False
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def Update(self, sender):
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"""Called by the RTD Server.
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Gives us a chance to check if our topic data needs to be
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changed (eg. check a file, quiz a database, etc)."""
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raise NotImplemented('subclass must implement')
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def Reset(self):
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"""Call when this topic isn't considered "dirty" anymore."""
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self.__dirty = False
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def GetValue(self):
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return self.__currentValue
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def SetValue(self, value):
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self.__dirty = True
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self.__currentValue = value
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def HasChanged(self):
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return self.__dirty
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# -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
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######################################
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# Example classes
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######################################
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class TimeServer(ExcelRTDServer):
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"""Example Time RTD server.
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Sends time updates back to excel.
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example of use, in an excel sheet:
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=RTD("Python.RTD.TimeServer","","seconds","5")
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This will cause a timestamp string to fill the cell, and update its value
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every 5 seconds (or as close as possible depending on how busy excel is).
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The empty string parameter denotes the com server is running on the local
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machine. Otherwise, put in the hostname to look on. For more info
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on this, lookup the Excel help for its "RTD" worksheet function.
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Obviously, you'd want to wrap this kind of thing in a friendlier VBA
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function.
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Also, remember that the RTD function accepts a maximum of 28 arguments!
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If you want to pass more, you may need to concatenate arguments into one
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string, and have your topic parse them appropriately.
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"""
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# win32com.server setup attributes...
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# Never copy the _reg_clsid_ value in your own classes!
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_reg_clsid_ = '{EA7F2CF1-11A2-45E4-B2D5-68E240DB8CB1}'
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_reg_progid_ = 'Python.RTD.TimeServer'
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_reg_desc_ = "Python class implementing Excel IRTDServer -- feeds time"
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# other class attributes...
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INTERVAL = 0.5 # secs. Threaded timer will wake us up at this interval.
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def __init__(self):
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super(TimeServer, self).__init__()
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# Simply timer thread to ensure we get to update our topics, and
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# tell excel about any changes. This is a pretty basic and dirty way to
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# do this. Ideally, there should be some sort of waitable (eg. either win32
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# event, socket data event...) and be kicked off by that event triggering.
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# As soon as we set up shop here, we _must_ return control back to excel.
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# (ie. we can't block and do our own thing...)
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self.ticker = threading.Timer(self.INTERVAL, self.Update)
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def OnServerStart(self):
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self.ticker.start()
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def OnServerTerminate(self):
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if not self.ticker.finished.isSet():
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self.ticker.cancel() # Cancel our wake-up thread. Excel has killed us.
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def Update(self):
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# Get our wake-up thread ready...
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self.ticker = threading.Timer(self.INTERVAL, self.Update)
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try:
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# Check if any of our topics have new info to pass on
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if len(self.topics):
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refresh = False
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for topic in self.topics.values():
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topic.Update(self)
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if topic.HasChanged():
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refresh = True
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topic.Reset()
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if refresh:
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self.SignalExcel()
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finally:
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self.ticker.start() # Make sure we get to run again
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def CreateTopic(self, TopicStrings=None):
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"""Topic factory. Builds a TimeTopic object out of the given TopicStrings."""
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return TimeTopic(TopicStrings)
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class TimeTopic(RTDTopic):
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"""Example topic for example RTD server.
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Will accept some simple commands to alter how long to delay value updates.
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Commands:
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* seconds, delay_in_seconds
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|
|
* minutes, delay_in_minutes
|
||
|
|
* hours, delay_in_hours
|
||
|
|
"""
|
||
|
|
def __init__(self, TopicStrings):
|
||
|
|
super(TimeTopic, self).__init__(TopicStrings)
|
||
|
|
try:
|
||
|
|
self.cmd, self.delay = self.TopicStrings
|
||
|
|
except Exception as E:
|
||
|
|
# We could simply return a "# ERROR" type string as the
|
||
|
|
# topic value, but explosions like this should be able to get handled by
|
||
|
|
# the VBA-side "On Error" stuff.
|
||
|
|
raise ValueError("Invalid topic strings: %s" % str(TopicStrings))
|
||
|
|
|
||
|
|
#self.cmd = str(self.cmd)
|
||
|
|
self.delay = float(self.delay)
|
||
|
|
|
||
|
|
# setup our initial value
|
||
|
|
self.checkpoint = self.timestamp()
|
||
|
|
self.SetValue(str(self.checkpoint))
|
||
|
|
|
||
|
|
def timestamp(self):
|
||
|
|
return datetime.datetime.now()
|
||
|
|
|
||
|
|
def Update(self, sender):
|
||
|
|
now = self.timestamp()
|
||
|
|
delta = now - self.checkpoint
|
||
|
|
refresh = False
|
||
|
|
if self.cmd == "seconds":
|
||
|
|
if delta.seconds >= self.delay:
|
||
|
|
refresh = True
|
||
|
|
elif self.cmd == "minutes":
|
||
|
|
if delta.minutes >= self.delay:
|
||
|
|
refresh = True
|
||
|
|
elif self.cmd == "hours":
|
||
|
|
if delta.hours >= self.delay:
|
||
|
|
refresh = True
|
||
|
|
else:
|
||
|
|
self.SetValue("#Unknown command: " + self.cmd)
|
||
|
|
|
||
|
|
if refresh:
|
||
|
|
self.SetValue(str(now))
|
||
|
|
self.checkpoint = now
|
||
|
|
|
||
|
|
if __name__ == "__main__":
|
||
|
|
import win32com.server.register
|
||
|
|
|
||
|
|
# Register/Unregister TimeServer example
|
||
|
|
# eg. at the command line: excelrtd.py --register
|
||
|
|
# Then type in an excel cell something like:
|
||
|
|
# =RTD("Python.RTD.TimeServer","","seconds","5")
|
||
|
|
win32com.server.register.UseCommandLine(TimeServer)
|