PySharpInventor - Autodesk Inventor Automation for Python

This library aims to simplify writing .NET/CLR Automation scripts for Autodesk Inventor with Python.

It talks to Inventor through the official .NET Interop assembly (Autodesk.Inventor.Interop.dll) using pythonnet, so you get the full, typed Inventor API from Python.

A Geneva drive generated by examples/geneva_mechanism.py.

Why pythonnet instead of win32com?

Most Python examples for Inventor use win32com, which talks to Inventor through late-bound COM dispatch. PySharpInventor uses Autodesk's official .NET Interop assembly instead:

• The same API as C# and VB.NET add-ins. Types, enums and method signatures match Autodesk's .NET samples and API help, so they translate to Python almost line by line.
• Real interface casting. InventorInterop.Circle(edge.Geometry) gives you a typed Circle; with win32com you need generated makepy wrappers and CastTo.
• Enums without code generation. InventorInterop.CurveTypeEnum.kCircleCurve works directly; no gencache.EnsureDispatch step to get constants.
• Inspectable objects. dir() on an object lists the members of its interface.

from pysharpinventor import Inventor, InventorInterop

inv = Inventor()
part = InventorInterop.PartDocument(inv.doc)
edge = part.ComponentDefinition.SurfaceBodies[1].Edges[1]

curve_type, curve = edge.cast_edge_geometry()
if curve_type == InventorInterop.CurveTypeEnum.kCircleCurve:
    print(curve.Radius)

Requires:

• Windows
• Python 3
• pythonnet>=3.0.0
• Autodesk Inventor (2020+)

Features:

• Dynamic Inventor version detection (picks the newest installed version)
• Lazy loading of the Interop assembly, so modules can be imported in any order
• .NET/CLR interface to Inventor API
• Document type casting (Part, Assembly, Drawing, Presentation)
• Geometry casting for edges and faces (LineSegment, Circle, Plane, Cylinder, ...)
• Extension methods on Inventor objects, e.g. edge.cast_edge_geometry()
• CadQuery-style string selectors, e.g. body.select_faces(">Z"), face.select_edges("%CIRCLE")
• Custom error handling with specific exceptions
• Support for connecting to active Inventor instances or creating new ones

Installation:

pip install pysharpinventor

For development, install from a clone in editable mode:

git clone https://github.com/Nandhakumarpro/PySharpInventor.git
cd pysharpinventor
pip install -e .

Usage Example:

from pysharpinventor import Inventor, InventorInterop

# Connect to active Inventor instance
inv = Inventor()

# Or create new instance if Inventor is not running
inv = Inventor(create_if_not_exists=True)

# Or point at a specific Inventor Interop DLL
inv = Inventor(inventor_path=r"C:\Program Files\Autodesk\Inventor 2025\Bin\Public Assemblies\Autodesk.Inventor.Interop.dll")

# Access active document
doc = inv.doc

# Cast document to specific type
part_doc = inv.cast_document(doc, InventorInterop.PartDocument)

# Or auto-detect document type
casted_doc = inv.cast_document(doc)

The Inventor object

Inventor(create_if_not_exists=False, visible=True, inventor_path=None)

• create_if_not_exists - start a new Inventor if none is running.
• visible - whether a newly started Inventor window is visible.
• inventor_path - path to Autodesk.Inventor.Interop.dll. When omitted, the newest installation under C:\Program Files\Autodesk\Inventor * is used.

Properties and methods:

• inv.app (alias inv.Application) - the Inventor.Application. Connects on first use.
• inv.doc (alias inv.ActiveDocument) - the active document.
• inv.cast_document(document, target_type=None) - cast a document to PartDocument, AssemblyDocument, DrawingDocument or PresentationDocument. Without target_type the type is detected from document.DocumentType.

InventorInterop

InventorInterop is the Inventor .NET namespace (Inventor.* in C#). Use it for classes and enums:

from pysharpinventor import InventorInterop

InventorInterop.PartDocument
InventorInterop.SurfaceTypeEnum.kPlaneSurface

It is safe to import anywhere, at any time. The Interop assembly is loaded the first time an attribute is accessed. If you need a custom DLL path, create Inventor(inventor_path=...) before touching InventorInterop; once loaded, the assembly cannot be swapped for another version in the same process.

Geometry casting

Edge.Geometry and Face.Geometry are returned by the API as a bare System.__ComObject. The helpers in pysharpinventor.geometry read the geometry type and cast it to the matching Inventor class:

from pysharpinventor.geometry import cast_edge_geometry, cast_face_geometry

body = part_doc.ComponentDefinition.SurfaceBodies[1]

curve_type, curve = cast_edge_geometry(body.Edges[1])
if curve_type == InventorInterop.CurveTypeEnum.kCircleCurve:
    print(curve.Radius)

surface_type, surface = cast_face_geometry(body.Faces[1])
if surface_type == InventorInterop.SurfaceTypeEnum.kCylinderSurface:
    print(surface.Radius, surface.AxisVector.X, surface.AxisVector.Y, surface.AxisVector.Z)

Edge curve type	Geometry class
kLineCurve	Line
kLineSegmentCurve	LineSegment
kCircleCurve	Circle
kCircularArcCurve	Arc3d
kEllipseFullCurve	EllipseFull
kEllipticalArcCurve	EllipticalArc
kBSplineCurve	BSplineCurve
kPolylineCurve	Polyline3d

Face surface type	Geometry class
kPlaneSurface	Plane
kCylinderSurface	Cylinder
kEllipticalCylinderSurface	EllipticalCylinder
kConeSurface	Cone
kEllipticalConeSurface	EllipticalCone
kTorusSurface	Torus
kSphereSurface	Sphere
kBSplineSurface	BSplineSurface

For unknown types (kUnknownCurve / kUnknownSurface) Inventor usually cannot provide the geometry; the helpers then return None as the geometry. Use edge.Evaluator / face.Evaluator for such entities.

get_edge_curve_type(edge) and get_face_surface_type(face) return only the type.

Extension methods

After import pysharpinventor, the geometry helpers are also available as methods on Edge, EdgeProxy, Face and FaceProxy objects, similar to C# extension methods:

curve_type, curve = body.Edges[1].cast_edge_geometry()
surface_type, surface = body.Faces[1].cast_face_geometry()

You can attach your own functions the same way:

from pysharpinventor._interop import register_extension

def area(face):
    return InventorInterop.Face(face).Evaluator.Area

register_extension('Face', 'area', area)
body.Faces[1].area()

String selectors

Faces, edges and vertices can be selected with CadQuery-style selector strings:

body = part_doc.ComponentDefinition.SurfaceBodies[1]

top = body.select_faces(">Z")[0]          # highest face
holes = top.select_edges("%CIRCLE")        # circular edges of that face
vertical = body.select_edges("|Z and >X")  # vertical edges at max X
sides = body.select_faces("#Z exc (>X or <X)")  # side faces except the X ends

The same functions are available as select_faces, select_edges and select_vertices in pysharpinventor.selectors; they also accept a list of entities, so selections can be refined. Results are typed (Face, Edge, Vertex) and returned in collection order.

Selector	Selects
>Z / <Z	farthest / nearest along the direction, by bounding-box centre
>Z[1]	second-farthest group; >Z[-1] is the nearest group
|Z	planar faces with normal parallel to Z, straight edges along Z
#Z	planar faces with normal perpendicular to Z, straight edges perpendicular to Z
+Z / -Z	planar faces whose outward normal points along / against Z
%PLANE	face types: PLANE, CYLINDER, CONE, SPHERE, TORUS, BSPLINE
%CIRCLE	edge types: LINE, CIRCLE, ELLIPSE, BSPLINE, POLYLINE
>(1, 1, 0)	any direction vector in place of X, Y, Z

Combine selectors with and, or, not, exc and parentheses (precedence not > and > or > exc). Each part of and is evaluated on the full set, so >X and >Z is empty unless one entity is both the farthest in X and the highest. Entities whose centres lie within 1e-4 cm along the direction count as one group, and >Z returns all of them. A tall vertical face can rank above a lower horizontal one, because its centre is higher.

Things to know

• Units. The Inventor API works in internal units: centimetres for length and radians for angles, regardless of the document's display units.
• Indexing is 1-based. body.Faces[1] is the first face.
• Iterating collections returns untyped objects. for e in body.Edges yields System.__ComObject values, which do not have the typed properties or extension methods. Cast them first: InventorInterop.Edge(e). Indexing (body.Edges[1]) returns typed objects.
• Plane normals may point into the solid. Plane.Normal is not guaranteed to be the outward direction of a face. Flip it when face.IsParamReversed is True.
• .NET API names differ from VBA in places. For example, use ExtrudeFeatures.Add(definition) rather than AddByDefinition.

Errors

• InventorVersionNotFoundError - the Interop DLL could not be found. Pass inventor_path.
• InventorConnectionError - pythonnet is missing, the DLL failed to load, or Inventor is not running (and create_if_not_exists is False).

Both can be imported from pysharpinventor.

Examples

Run the examples from the repository root.

examples/hello_world.py creates a new part containing a 5 cm cube and prints each face's type, area and outward normal:

python -m examples.hello_world

examples/selectors_demo.py creates a stepped block with a hole, prints what various string selectors pick, and then uses selectors to place a fillet, a chamfer and a sketch:

python -m examples.selectors_demo

examples/geneva_mechanism.py creates a 4-slot external Geneva drive as a multi-body part: a drive wheel with pin and locking disc, and a slotted Geneva wheel, placed in the locked position. All dimensions are derived from the slot count, centre distance and pin size, and can be changed through GenevaDesign:

python -m examples.geneva_mechanism

from pysharpinventor import Inventor
from examples.geneva_mechanism import GenevaDesign, create_geneva_mechanism

design = GenevaDesign(slots=6, center_distance=12.0, pin_radius=0.4)
part_doc, drive, geneva = create_geneva_mechanism(Inventor(), design)

Links

• Source code at GitHub