Help accessing COM .dll from Python

[Chris Angelico]

Quoting his entire text for the benefit of Mr Dietrich, who is
apparently having trouble reading it. (He's right though, plain text
is a lot easier to work with.)

On Sat, Dec 1, 2012 at 8:51 PM, Steve Simmons <square.steve at gmail.com> wrote:
> First time post - be gentle with me :-)
>
> I am trying to write a Python script to access a scanning device.  I have an
> SDK for the scanner but the documentation is a bit limited and the supplier
> doesn't support Python (but Python is the best option for me in the current
> circumstances).
>
> The SDK revolves around a .dll file that is described as a 'COM Object' but
> the text also implies that it can be accessed directly - "If you don’t use
> the COM interface in your application and use the SDK files directly like in
> VC++ then you don’t need to install these files on the destination
> computer".  If I look inside the .dll (thanks PE Explorer!), I see
> DllCanUnload, DllGetClassObject, DllRegisterServer and DllUnregisterServer
> in the 'Export' view.  If I look at the 'Import' view, I can see the names
> of a bunch of .dll files and the names of the functions/methods I want to
> call.  So I concluded that  DllGetClassObject would be my friend.
>
> However, I've read various tutorials on using .dll and COM (ctypes,
> comtypes, and the Python documentation) and I've ended up more confused than
> when I started.  I expected to be using COM but all the examples seem to
> revolve around automating excel or outlook.
>
> I'd be really grateful for some hints on what direction I should be headed
> and a pointer to a relevant tutorial.
>
> Simmo

Yeah, ctypes isn't all that easy to work with I'm afraid. Ultimately,
your problem is with your scanner's SDK; if it's poorly documented,
it's not going to be any easier working from Python than it would be
from C. I would advise following their non-COM instructions as closely
as you can, and seeing where that leads you. If their docs are online,
post us a link; it's possible someone here may be familiar with it, or
at very least be able to help you with the translation to Python.

Good luck!

ChrisA