Python - VBA - HTML Help - COM Callable Python class runs *.chm decompiler.

I have many old *.chm compiled help files on my computer and for some reason the help viewer is bust. I am considering writing (Python) code which will upgrade these *.chm files into ebooks. The first module is given here, it will run the Microsoft HTML Help executable (hh.exe) to decompile a *.chm file into its constituent html files all within working subdirectories in the %temp% folder.

Submitting to Code Review

I might very well complete a full application and place in github. This means I need to raise my Python standards and so I have submitted this module to codereview.stackexchange.com

The HelpFileDecompiler Python class

Here is the Python code

class HelpFileDecompiler(object):
    _reg_clsid_ = "{4B388A08-8CAB-4568-AF78-47032744A368}"
    _reg_progid_ = 'PythonInVBA.HelpFileDecompiler'
    _public_methods_ = ['DecompileHelpFileMain']

    def DecompileHelpFileMain(self, sHelpFile):
        import os.path
        eg = ", e.g. 'c:\\foo.chm'"
        if not isinstance(sHelpFile, str):
            raise Exception("sHelpFile needs to be a string" + eg)
        if len(sHelpFile) == 0:
            raise Exception("sHelpFile needs to be a non-null string" + eg)
        if sHelpFile.lower()[-4:] != ".chm":
            raise Exception("sHelpFile needs to end with '.chm' " + eg)
        if not os.path.isfile(sHelpFile):
            raise Exception("sHelpFile " + sHelpFile + " not found")

        self.BuildTmpDirectory()
        sCopiedFile = self.CopyChmFileToTempAppPath(sHelpFile)
        self.DecompileHelpFile(sCopiedFile)

    def BuildTmpDirectory(self):
        import os
        import os.path
        sTempAppPath = os.path.join(os.environ['tmp'], 'HelpFileDecompiler')

        if not os.path.isdir(sTempAppPath):
            os.mkdir(sTempAppPath)

    def CopyChmFileToTempAppPath(self, sHelpFile):
        import shutil
        import os.path
        sDestFile = os.path.join(os.environ['tmp'], 'HelpFileDecompiler',
                                    os.path.basename(sHelpFile))
        shutil.copyfile(sHelpFile, sDestFile)
        return sDestFile

    def DecompileHelpFile(self, sHelpFile):
        import win32api
        import subprocess
        import os.path

        if not os.path.isfile(sHelpFile):
            raise Exception("sHelpFile " + sHelpFile + " not found")

        sDecompiledFolder = os.path.join(
            os.environ['tmp'],
            'HelpFileDecompiler',
            os.path.basename(sHelpFile).split(".")[0])

        if not os.path.isdir(sDecompiledFolder):
            os.mkdir(sDecompiledFolder)

        sHELPEXE = "C:\Windows\hh.exe"
        if not os.path.isfile(sHELPEXE):
            raise Exception("sHELPEXE " + sHELPEXE + " not found")

        # Not allowed to quote arguments to HH.EXE
        # so we take the short path to eliminate spaces
        sHelpFileShort = win32api.GetShortPathName(sHelpFile)
        sDecompiledFolderShort = win32api.GetShortPathName(sDecompiledFolder)

        # so now we can run the decompiler
        subprocess.run([sHELPEXE, '-decompile',
                        sDecompiledFolderShort, sHelpFileShort])


if __name__ == '__main__':
    print ("Registering COM servers...")
    import win32com.server.register
    win32com.server.register.UseCommandLine(HelpFileDecompiler)

    helpFile=("C:\\Program Files\\Microsoft Office 15\\root\\vfs\\"
                "ProgramFilesCommonX86\\Microsoft Shared\\VBA\\VBA7.1\\"
                "1033\\VBLR6.chm")
    test = HelpFileDecompiler()
    test.DecompileHelpFileMain(helpFile)

Here is some test VBA client code

Option Explicit

Sub Test()

    Dim obj As Object
    Set obj = VBA.CreateObject("PythonInVBA.HelpFileDecompiler")
    
    obj.DecompileHelpFileMain "C:\Program Files\Microsoft Office 15\root\vfs\" & _
              "ProgramFilesCommonX86\Microsoft Shared\VBA\VBA7.1\" & _
              "1033\VBLR6.chm"

End Sub