This is my first post in Steemit, I thought to write the first post regarding DGB but, due to recent issues that I met during my job, I decide to post a little trick about ActiveX/COM and how to use variant array in Python.
Synopsis
Recently I had to write a script to automate a several operation in a several hundreds file of AutoCAD. I decided to use Python. In the usual way I'll code with VBA or Lisp but this time I would to try if there will be any advantage using python and ... it was!!!!
To get started
First of all I looked for a Python module (i.e. library) that "library aimed to simplify writing ActiveX Automation scripts for AutoCAD with Python", oh oh but it is pyautocad and it is what I need. After install it I start to code.
AutoCAD application wrapper
The first is a simple wrapper that instantiate the COM server object o AutoCAD:
from pyautocad import *
def getAutocadApplication(create_if_not_exists=True):
''' Return the Autocad application Object'''
acad = Autocad(create_if_not_exists, visible=True)
if acad is None:
return None
else:
return acad.app
Loading DWG and the problem with variant array.
The code to load a DWG document is very simple:
acadApp = getAutocadApplication()
acadDoc = acadApp.Documents.Open(path.join(source_path, filename))
and to retrieve the BoundingBox, from AutoCAD ActiveX documentation:
# Signature
object.GetBoundingBox MinPoint, MaxPointobject
[object]
Type: All drawing objects, AttributeReference, Dimension
The objects this method applies to.
[MinPoint[]
Access: Output-only
Type: Variant (three-element array of doubles)
The 3D WCS coordinates specifying the minimum point of the object's bounding box.
[MaxPoint]
Access: Output-only
Type: Variant (three-element array of doubles)
The 3D WCS coordinates specifying the maximum point of the object's bounding box.
and my question is: How to pass an variant array to a COM object (in Python)?
Solution
After several hours passed to search in the Web (see Contributors below) I implemented the follow:
def GetBoundingBox(entity):
# Create 3-d 'Variant' array of 'd'-ouble
A = automation.VARIANT(array('d', [0,0,0]))
B = automation.VARIANT(array('d', [0,0,0]))
# Get the reference / address
vA = byref(A)
vB = byref(B)
# Call the method from COM object
entity.GetBoundingBox(vA, vB)
# Return two points as 3-d
return (A.value, B.value)
and this is the solution with the amazing NumPy module:
def GetBoundingBox(entity):
# Create 3-d 'Variant' array of 'd'-ouble
A = np.Array([0,0,0], dtype=double)
B = np.Array([0,0,0], dtype=double)
# Call the method from COM object
entity.GetBoundingBox(A, B)
# Return two points as 3-d
return (A, B)
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STOPhey d-man, I saw that you downvoted my posts. I understand that you thought you did the right thing, but please(!) understand that I'm not a pedophile and this a huge misunderstanding. I've written a short post about this whole sitation. Would you mind reading through it? https://steemit.com/steemit/@therealwolf/i-feel-humiliated-and-bullied
I don't like to be marked as something I am not . Thank you!!
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