[python-win32] Why doesn't dir() list COM object properties, only methods?

[Jeremy Herbert]

Hi Tim,

Sorry, I did not intend for my message to be interpreted as overly
harsh :) Is there any way to introspect the properties of the objects
at runtime using python? They are present in the makepy file under
_prop_map_get_.

Thanks,
Jeremy Herbert


On Mon, Sep 15, 2014 at 7:33 PM, Tim Roberts <timr at probo.com> wrote:
> Jeremy Herbert wrote:
>> I'm currently struggling a little with pywin32, and to me it seems
>> that the default python dir() behaviour is broken. For the record, I
>> am forcing early-binding.
>
> "Broken" is too harsh of a word.  What you're seeing here is more or
> less an impedance mismatch between two very different interfaces.
>
> The Python dir() function knows about Python objects living in the
> Python object space.  COM objects live in an entirely different space.
> Python, being cross-platform, doesn't have any internal knowledge about
> COM, which is strictly a Windows concept.
>
> The win32com code does its best to provide a bridge between those
> worlds, by providing a simulated Python object that satisfies most of
> the Python object requirements, but proxies its activities to the COM
> object it is wrapping.  In the case of early binding, the only way
> win32com can do that is by parsing the TLB to figure out the object
> layout.  If you look at the Python file generated by makepy, do you see
> the properties there?
>
> One interesting side note is that COM doesn't really have the notion of
> properties, because many languages don't support them.  When an object
> supports a Color property, that's actually implemented by having methods
> called get_Color and set_Color.  You might see if those are in the
> makepy file.
>
>
>> Note that both member functions and variables are present. When I run
>> dir() on a COM object instance however, it does not show any of the
>> member properties, just the member functions. So if the A class was
>> instantiated as an COM object, it would only show "hello" as well as
>> the builtins in the printout, and "member" would be missing.
>
> You do need to remember that you're not really looking at a COM object
> instance.  You're looking at a win32com proxy that is communicating with
> the COM object.  It's doing the best it can with the information it can
> extract, but if the TLB doesn't include everything, makepy can't make it up.
>
>
>> Given that I am trying to interact with Autodesk Inventor, and 90% of
>> the functionality of the COM interface is via properties, this is
>> quite frustrating! Is there any way to list all of the properties of a
>> COM object instance?
>
> Check the makepy file and see if they are present.
>
> --
> Tim Roberts, timr at probo.com
> Providenza & Boekelheide, Inc.
>
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