can not read attributes from block reference

[thengineer]

I'm trying to read block attributes:

from pyautocad import Autocad
acad =  Autocad()       

Reading other properties works fine:

In [89]: b.InsertionPoint
Out[89]: (3764.4951495785735, 745.3710248379173, 0.0)

However, when I want to query the attributes (which I'm actually interested in), I get an error message:

In [88]: b.GetAttributes()
---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-88-a01693316a19> in <module>()
----> 1 b.GetAttributes()

C:\ProgramFiles\Python27\lib\site-packages\comtypes\automation.pyc in __ctypes_from_outparam__(self)
    440     def __ctypes_from_outparam__(self):
    441         # XXX Manual resource management, because of the VARIANT bug:
--> 442         result = self.value
    443         self.value = None
    444         return result

C:\ProgramFiles\Python27\lib\site-packages\comtypes\automation.pyc in _get_value(self, dynamic)
    391             return value
    392         elif self.vt & VT_ARRAY:
--> 393             typ = _vartype_to_ctype[self.vt & ~VT_ARRAY]
    394             return cast(self._.pparray, _midlSAFEARRAY(typ)).unpack()
    395         else:

Did some research on Google, but my knowledge of COM is just too low to help myself here..

[thengineer]

I solved this by using win32com. In case anybody comes across the same problem (and wants to save a few hours of work):
https://gist.github.com/thengineer/7157510

[cfarrow]

I just opened an issue for this in the comtypes package, on which pyautocad is based. @thengineer, if you can provide more information about the KeyError, I may be able to fix this issue.

[thengineer]

@cfarrow: That's good to know someone is working on COM related things :)
However all that I could find out, was that comtypes doesnt handle the required data type within VT_arrays or something like this.
I wish I could help you more on this. (Well, at least I'm running AutoCAD, so I could test things)

[cfarrow]

I could test this out as well. I'll need AutoCAD, and so as much information that you can give me up front will help me make the most of a trial license. :)

[thengineer]

you will find the VBA Reference under C:\Program Files\Common Files\Autodesk Shared\acadauto.chm, which gives you a good overview of the object model in autocad.

The actual problematic things are the Attributes (= user definable key/value pairs) of the Blocks (or Block references actually). See my gist file posted above for how to access them with win32com.

If you need help creating such a block or need an example file, let me know.

[LiaungYip]

@thengineer : Your workaround using win32com is great.

[OndrejJanota]

Hi, I'm totally new in python (3 days) and I would like to create a program which rewrite block attributes. However, the script provided by thengineer (Here: https://gist.github.com/thengineer/7157510) doesn't work. I get this error (trying on Acad2017, drawing with only just one block with manualy defined block attribute):

Traceback (most recent call last):
File "E:\Python\Programs\Autocad\Blockreference\block.py", line 21, in
HasAttributes = entity.HasAttributes() # => tohle nějak nefunguje nevím proč
File "E:\Python\lib\site-packages\win32com\client_init_.py", line 473, in getattr
raise AttributeError("'%s' object has no attribute '%s'" % (repr(self), attr))
AttributeError: '<win32com.gen_py.AutoCAD/ObjectDBX Common 21.0 Type Library.IAcadEntity instance at 0x2236061099512>' object has no attribute 'HasAttributes'

Has anyone the same problem?
Thanks for the reply.

[Pilou59]

I've got the same issue, but using getattributes() method.

Here are my investigations...

[thengineer]

Interestingly I came across the same issue a few months ago. I ended up checking the existence of attributes using python's hasattr() before accessing attributes.

[lam2912]

I solved this by using win32com. In case anybody comes across the same problem (and wants to save a few hours of work): https://gist.github.com/thengineer/7157510

Please tell me: How to Setup Module Win 32???

[obook]

I solved this by using win32com. In case anybody comes across the same problem (and wants to save a few hours of work): https://gist.github.com/thengineer/7157510

Please tell me: How to Setup Module Win 32???

Install the win32com Python library (pip version)

pip install pypiwin32

Then reboot !

Usage

import win32com.client
acad = win32com.client.Dispatch("AutoCAD.Application")

for entity in acad.ActiveDocument.ModelSpace:
            if entity.EntityName == 'AcDbBlockReference':
                print(entity.Name)
                if entity.HasAttributes:
                    for attrib in entity.GetAttributes():
                        print("-> {}: {}".format(attrib.TagString, attrib.TextString))

Regards.

[chuongmep]

Update for anyone need to quick check :

import win32com.client

# Connect to AutoCAD
acad = win32com.client.Dispatch("AutoCAD.Application")

# Define output file path
output_file = "block_attributes_output.txt"

# Open file for writing
with open(output_file, "w", encoding="utf-8") as f:
    for entity in acad.ActiveDocument.ModelSpace:
        if entity.EntityName == 'AcDbBlockReference':
            # Write block name, layer, and handle
            f.write(f"Block Name: {entity.Name}\n")
            f.write(f"Layer: {entity.Layer}\n")
            f.write(f"Handle: {entity.Handle}\n")

            # Write attributes if they exist
            if entity.HasAttributes:
                for attrib in entity.GetAttributes():
                    f.write(f"  -> {attrib.TagString}: {attrib.TextString}\n")

            f.write("\n")  # Blank line between blocks

print(f"Output saved to {output_file}")