Accessing a dll from Python

[dcrespo]

Hi to all,

Can someone give me lights on how can I deal with dlls from python?

My main purpose is to get access to a Unitech PT600 Bar Code system. I
have the dll that works fine through Visual Basic. But I'm migrating to
Python, so I need a way to use the same dll, or a C library.

I tried to access a dll created by myself on Visual Basic. The dll just
have one function. It works perfect when using it on a VB project just
including it in the references configuration. But I can't access it
from python. I tried the ctypes module.

Thank you

Daniel

[Richie Hindle]

Re: Accessing a dll from Python


[Daniel][color=blue]
> I tried the ctypes module.[/color]

ctypes is the right way to do it. You need to post your code and whatever
errors you received. Here's an example of using ctypes to call a DLL:
[color=blue][color=green][color=darkred]
>>> from ctypes import *
>>> windll.user32.M essageBoxA(None , "Hello world", "ctypes", 0);[/color][/color][/color]

You use "windll" for stdcall functions (eg. the Windows API) and "cdll" for
cdecl functions. I don't know which one VB defaults to. If you get it
wrong, ctypes will give you an error talking about using the "wrong calling
convention".

--
Richie Hindle
richie@entrian. com

[Larry Bates]

Re: Accessing a dll from Python

If you want you can also take a look at something I wrote a while
ago (before ctypes was really well known). It has worked for me
with .DLLS form Castelle and Expervision that both have extensive
APIs. It is located here:

http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/146847

Larry Bates

dcrespo wrote:[color=blue]
> Hi to all,
>
> Can someone give me lights on how can I deal with dlls from python?
>
> My main purpose is to get access to a Unitech PT600 Bar Code system. I
> have the dll that works fine through Visual Basic. But I'm migrating to
> Python, so I need a way to use the same dll, or a C library.
>
> I tried to access a dll created by myself on Visual Basic. The dll just
> have one function. It works perfect when using it on a VB project just
> including it in the references configuration. But I can't access it
> from python. I tried the ctypes module.
>
> Thank you
>
> Daniel
>[/color]

[mku]

Re: Accessing a dll from Python

I used ctypes. It works really fine with DLLs.
have a lool at http://starship.python.net/crew/theller/ctypes
Martin

[Tim Roberts]

Re: Accessing a dll from Python

"dcrespo" <dcrespo@gmail. com> wrote:[color=blue]
>
>Can someone give me lights on how can I deal with dlls from python?
>
>My main purpose is to get access to a Unitech PT600 Bar Code system. I
>have the dll that works fine through Visual Basic. But I'm migrating to
>Python, so I need a way to use the same dll, or a C library.
>
>I tried to access a dll created by myself on Visual Basic. The dll just
>have one function. It works perfect when using it on a VB project just
>including it in the references configuration. But I can't access it
>from python. I tried the ctypes module.[/color]

Are you talking about VB6 or VB.NET? If you had to add a reference, then
it is either a COM interface or a managed code class. DLLs don't get in
through references -- they use the Declare statement.

COM interfaces are pretty easy to call in Python. Calling managed code is
almost impossible right now.
--
- Tim Roberts, timr@probo.com
Providenza & Boekelheide, Inc.

[Grant Edwards]

Re: Accessing a dll from Python

On 2005-10-20, dcrespo <dcrespo@gmail. com> wrote:
[color=blue]
> Can someone give me lights on how can I deal with dlls from python?[/color]

Use the ctypes module.
[color=blue]
> My main purpose is to get access to a Unitech PT600 Bar Code system. I
> have the dll that works fine through Visual Basic. But I'm migrating to
> Python, so I need a way to use the same dll, or a C library.[/color]

ctypes can call dll functions using either C or Pascal calling
conventsions.
[color=blue]
> I tried to access a dll created by myself on Visual Basic. The
> dll just have one function. It works perfect when using it on
> a VB project just including it in the references
> configuration. But I can't access it from python. I tried the
> ctypes module.[/color]

ctypes has always worked for me.

Sorry, I've no clue about anything VB-related unless it's
Victoria Bitter.

--
Grant Edwards grante Yow! I have a VISION! It's
at a RANCID double-FISHWICH on
visi.com an ENRICHED BUN!!

[Simon Brunning]

Re: Accessing a dll from Python

On 21/10/05, Grant Edwards <grante@visi.co m> wrote:[color=blue]
> Sorry, I've no clue about anything VB-related unless it's
> Victoria Bitter.[/color]

+1 QOTW.

--
Cheers,
Simon B,
simon@brunningo nline.net,

http://www.brunningonline.net/simon/blog/