Python for AutoLISP Users part 1:

[Danielm103]

I thought I might write some samples to help guide lisp users that are interested in trying out Python.

 

Long time lisp users will feel right at home using result buffers (DXF Lists). In PyRx, it’s wrappers around the old school C ADS functions, I.e. ads_entget, yay, like driving an F-150 with a toilet bowl plunger as the gear shift. In Python, most of these old functions reside in Db.Core

 

The resbuf* linked lists are wrapped into a list of tuples.. does this output look familiar?

 

from pyrx import Ap, Db, Ed, Ge

@Ap.Command()
def doit0() -> None:
    
    #entsel with a filter
    ps, id, _ = Ed.Editor.entSel("\nPick it: ", Db.Line.desc())
    if ps != Ed.PromptStatus.eOk:
        raise RuntimeError("oof {}:".format(ps))

    #get the result buffer 
    rb = Db.Core.entGet(id)
    print(rb)
    # [
    # (-1, PyDb.ObjectId(1de8bf954d0)), 
    # (0, 'LINE'), 
    # (330, PyDb.ObjectId(1de8bf9a1f0)), 
    # (5, '265'), 
    # (100, 'AcDbEntity'),
    # (67, 0), 
    # (410, 'Model'), 
    # (8, '0'), 
    # (100, 'AcDbLine'),
    # (10, PyGe.Point3d(0.00000000000000,0.00000000000000,0.00000000000000)), 
    # (11, PyGe.Point3d(100.00000000000000,100.00000000000000,0.00000000000000)),
    # (210, PyGe.Point3d(0.00000000000000,0.00000000000000,1.00000000000000))
    # ]

 

[Danielm103]

In Python, there isn’t an assoc function, we can iterate through and search for a DXF code

 

from pyrx import Ap, Db, Ed, Ge


@Ap.Command()
def doit1() -> None:
    
    # entsel with a filter
    ps, id, _ = Ed.Editor.entSel("\nPick it: ", Db.Line.desc())
    if ps != Ed.PromptStatus.eOk:
        raise RuntimeError("oof {}:".format(ps))

    # get the result buffer 
    rb = Db.Core.entGet(id)

    # 1. Analog to Lisp: (assoc 8 rb) -> Returns the full pair (8, "LayerName")
    dxf_code, value = next((item for item in rb if item[0] == 8), None)
    
    # 2. Extract just the value safely
    if dxf_code:
        print(f"The layer is: {value}")

 

[Danielm103]

In Python, tuples are immutable, so if we want to modify the list, you have to replace it. In this sample we modify the start and end of a line

 

from pyrx import Ap, Db, Ed, Ge

@Ap.Command()
def doit3() -> None:
    
    #entsel with a filter
    ps, id, _ = Ed.Editor.entSel("\nPick it: ", Db.Line.desc())
    if ps != Ed.PromptStatus.eOk:
        raise RuntimeError("oof {}:".format(ps))

    #get the result buffer 
    rb = Db.Core.entGet(id)

    # Loop through the result buffer list and modify matching DXF codes
    for i, item in enumerate(rb):
        dxf_code = item[0]
        if dxf_code == 10:
            rb[i] = (10, Ge.Point3d(0, 0, 0))
        elif dxf_code == 11:
            rb[i] = (11, Ge.Point3d(100, 100, 0))

    # Apply changes back to the AutoCAD database
    Db.Core.entMod(rb)

 

[Danielm103]

This might be better example, maybe similar to the COND expression?

 

from pyrx import Ap, Db, Ed, Ge

@Ap.Command()
def doit4() -> None:
    ps, id, _ = Ed.Editor.entSel("\nPick it: ", Db.Line.desc())
    if ps != Ed.PromptStatus.eOk:
        raise RuntimeError("oof {}:".format(ps))
    
    #get the result buffer 
    rb = Db.Core.entGet(id)
    
    # Process the result buffer using structural pattern matching
    updated_rb = []
    for item in rb:
        match item:
            case (10, _):
                updated_rb.append((10, Ge.Point3d(0, 0, 0)))
            case (11, _):
                updated_rb.append((11, Ge.Point3d(100, 100, 0)))
            case _:
                updated_rb.append(item)
         
    # Apply changes back to the AutoCAD database       
    Db.Core.entMod(updated_rb)

 

[Danielm103]

And top it off with entMake

 

from pyrx import Ap, Db, Ed, Ge

@Ap.Command()
def doit5() -> None:
    Db.Core.entMake([(0 , "LINE"),(10, Ge.Point3d(0, 0, 0)),(11, Ge.Point3d(100, 100, 0))]) 

 

Edited 4 hours ago by Danielm103

[Danielm103]

There are some items in the database, where the only option is to use entGet, I.e. ACAD_FIELDLIST is not exposed to ARX

See: https://www.cadtutor.net/forum/topic/99220-python-change-precision-of-all-fields-in-a-drawing/

[troggarf]

Daniel,

For total LISP hacks like me who barely get by piecing together LISP code that we find online. I don't even know where to begin with trying to utilize the awesome python code that you share.

It isn't as easy as opening Notepad and copying and pasting code and then saving as a different filetype. Then dragging that file into your drawing area to load and use. So I am asking as a total beginner, Where do I start? Is there a simple breakdown with instructions for us curious newbies?

 

Thanks

~Greg

 

BTW - Thanks for all the stuff that you share