Kelie schrieb:
> Hello,
>
> First of all, I suppose most users on this list would have no interest in this
> topic. But I'm posting it anyway because it has puzzled for quite a while and
> finally thanks to Thomas who found a solution. I also want to thank Ed Blake
> who
> showed me a solution with win32com.
>
> The question started with how to pass the right parameter to AutoCAD's
> AddPoint
> function. It is supposed to be Variant (three-element array of doubles)
> according to the VBA API reference. The array.array function was the answer:
>
> import array
> import comtypes.client
> acadApp = comtypes.client.GetActiveObject("AutoCAD.Application")
> ms = acadApp.ActiveDocument.ModelSpace
> pt = array.array('d', [0,0,0])
> ms.AddPoint(pt)
> print "Done."
>
The reason for this is the following. Acad declares the AddPoint method with
this signature:
[id(0x0000061a), helpstring("Creates a Point object at a given location"),
helpcontext(0x00010097)]
HRESULT _stdcall AddPoint(
[in] VARIANT Point,
[out, retval] IAcadPoint** pPoint);
so it expects a VARIANT specifying the Point coordinates.
A VARIANT can contain a lot of different data types; it is unspecified above
that Autocad only accepts a VARIANT containing a SAFEARRAY of doubles.
By default, when you pass a Python sequence (tuple or list) for this parameter
comtypes constructs a VARIANT containing a SAFEARRAY of VARIANTS. When you pass
an array.array instance for the parameter, comtypes constructs a VARIANT
containing
a SAFEARRAY of type VT_R8 if the typecode of the array is 'd' (double), VT_R4
for the
typecode 'f' (float), and so on.
I assume this is the same for a lot of com servers requiring a VARIANT
containing a SAFEARRAY.
Thomas
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