Sources_For_Win/ParaView/Lib/site-packages/win32com/demos/trybag.py

import pythoncom
from win32com.server import util
from win32com.server import exception

VT_EMPTY = pythoncom.VT_EMPTY

class Bag:
  _public_methods_ = [ 'Read', 'Write' ]
  _com_interfaces_ = [ pythoncom.IID_IPropertyBag ]

  def __init__(self):
    self.data = { }

  def Read(self, propName, varType, errorLog):
    print("read: name=", propName, "type=", varType)
    if propName not in self.data:
      if errorLog:
        hr = 0x80070057
        exc = pythoncom.com_error(0, "Bag.Read", "no such item", None, 0, hr)
        errorLog.AddError(propName, exc)
      raise exception.Exception(scode=hr)
    return self.data[propName]

  def Write(self, propName, value):
    print("write: name=", propName, "value=", value)
    self.data[propName] = value


class Target:
  _public_methods_ = [ 'GetClassID', 'InitNew', 'Load', 'Save' ]
  _com_interfaces_ = [ pythoncom.IID_IPersist,
                       pythoncom.IID_IPersistPropertyBag ]

  def GetClassID(self):
    raise exception.Exception(scode=0x80004005)	# E_FAIL

  def InitNew(self):
    pass

  def Load(self, bag, log):
    print(bag.Read('prop1', VT_EMPTY, log))
    print(bag.Read('prop2', VT_EMPTY, log))
    try:
      print(bag.Read('prop3', VT_EMPTY, log))
    except exception.Exception:
      pass

  def Save(self, bag, clearDirty, saveAllProps):
    bag.Write('prop1', 'prop1.hello')
    bag.Write('prop2', 'prop2.there')

class Log:
  _public_methods_ = [ 'AddError' ]
  _com_interfaces_ = [ pythoncom.IID_IErrorLog ]

  def AddError(self, propName, excepInfo):
    print("error: propName=", propName, "error=", excepInfo)

def test():
  bag = Bag()
  target = Target()
  log = Log()

  target.Save(bag, 1, 1)
  target.Load(bag, log)

  comBag = util.wrap(bag, pythoncom.IID_IPropertyBag)
  comTarget = util.wrap(target, pythoncom.IID_IPersistPropertyBag)
  comLog = util.wrap(log, pythoncom.IID_IErrorLog)

  comTarget.Save(comBag, 1, 1)
  comTarget.Load(comBag, comLog)

if __name__ == '__main__':
  test()