SwPy — Python for SOLIDWORKS

SwPy embeds real CPython inside SOLIDWORKS. Write and run Python against the live SOLIDWORKS API from a task-pane IDE, use a Pythonic layer for everyday jobs, install any pip package, and drive SOLIDWORKS from Jupyter or other applications.

# r: openpyxl                                      # pip packages on demand
with model.batch():                                # many edits, one rebuild
    model.dims["D1@Boss-Extrude1"] = 25 * mm       # SI units, no casts
    model.globals["Width"] = 120 * mm
model.faces.planar().normal(Z).largest().select()  # geometry queries
print(model.mass["mass"], "kg")

Contents

• Features
• Requirements
• Installation
• Quick start
• Documentation
• How it works
• Project structure
• Development
• Security
• Changelog
• License

Features

In-process Python

• CPython 3.12 running inside SLDWORKS.exe via pythonnet: API calls take microseconds, not the hundreds of milliseconds of out-of-process COM.
• Ships its own embeddable Python runtime; no Python install and no admin rights needed.
• Persistent sessions, live print output, notebook-style results, tracebacks that show only your code.

Task-pane IDE

• Tabs, recent files and automatic backups of untitled scripts.
• IntelliSense from the live session: completion for real objects (doc., model., swconst.), following SOLIDWORKS API return types without running anything. Also signature help, hover info, and F1 → official API help.
• Syntax checking as you type, runtime errors marked on the failing line, and double-click on a traceback line to jump to it.
• Find/replace with regex, go to line, multi-caret editing, comment toggle, line moves, code folding, brace matching, auto-closing pairs.
• Light and dark themes, a REPL with history and Tab completion.

Pythonic API (swpy.model)

• SI units everywhere: 30 * mm, to(value, deg).
• Dimensions and global variables as dictionaries, and model.batch() for one rebuild after many edits.
• Mass properties, features, default planes that work with any template.
• Chainable face/edge queries: model.faces.cylindrical().radius(5 * mm).edges.circular().select().
• Build geometry: with model.sketch(model.planes.front) as s: s.rect(...), model.extrude(s, 20 * mm), cut, revolve, fillet, chamfer, shell; assemblies (add_component, mate, bom); drawings (create_drawing) and model.export("part.step" | "drawing.pdf" ...).

Full SOLIDWORKS API

• Automatic typing: no casts. Objects expose the members of every interface they implement.
• All enums (swconst), typed casts (sldworks.IFoo), Python lists for arrays, tuples for out-parameters.
• Every SOLIDWORKS API library: Simulation, Motion, DimXpert, Routing, Costing, PDM, Document Manager, Utilities, Toolbox ... (cosworks.ICosmosWorks(obj), swcommands.swCommands_e).

Events

• @on(doc, "rebuild"), on(sw, "active_doc", fn): Python handlers for any SOLIDWORKS event, isolated from errors and removed automatically on Reset, document close and unload.

Tools for your team

• Every .py in Documents\SwPy\Scripts becomes a one-click tool (pane menu; SwPy toolbar and CommandManager tab with a machine-wide install); startup\ scripts run when SOLIDWORKS starts.
• ui.progress (Esc cancels long loops), ui.message, ui.ask, ui.prompt, file and folder dialogs.

Packages and automation

• # r: numpy, pandas installs pip packages per user on first run.
• swpy.client: drive SOLIDWORKS from Jupyter or any Python. Excel VBA and C# can call the same COM entry point.

Requirements

OS	Windows 10/11 x64
SOLIDWORKS	2020 or newer (developed and tested on 2020 SP1)
Python	none for users (bundled 3.12); Python 3.10+ with pywin32 for the remote client
Rights	standard user; admin only for optional machine-wide auto-load

Installation

1. Download SwPy-x.y.z.zip from the latest release and unzip it to a permanent folder (e.g. %LOCALAPPDATA%\Programs\SwPy), or build from source.

2. In that folder, register SwPy for your Windows user and create the SOLIDWORKS + SwPy shortcut:

   powershell -ExecutionPolicy Bypass -File tools\install.ps1

3. Start SOLIDWORKS with the SOLIDWORKS + SwPy shortcut and open the SwPy - Python tab of the task pane.

Options: -Machine also registers SwPy machine-wide, so SOLIDWORKS loads it at every start (needs admin). -Uninstall removes everything.

Quick start

Open a part, type into the editor and press F5:

for f in model.features():
    print(f.GetTypeName2().ljust(16), f.Name)
print("volume:", round(to(model.mass["volume"], mm**3)), "mm^3")

From Jupyter or another Python (pip install -e .[client] from this repository):

import swpy.client as swc
sw = swc.connect()
sw.eval("model.mass['mass']")        # -> 0.12

Documentation

The user guide (also as a website: https://muerus.github.io/SolidWorks-Python/) covers everything:

Getting started	Install, first script, where files live
The editor	IntelliSense, shortcuts, tabs, find/replace
Scripting basics	Predefined names, sessions, output, units
The model API	Dimensions, globals, batch, mass, face/edge queries
SOLIDWORKS API from Python	Auto-typing, casts, enums, arrays, out-parameters, porting VBA
Packages	# r: requirements
Remote control	Jupyter, scripts, Excel, C#
Recipes	Parts from scratch, studies, exports, properties, assemblies
Troubleshooting	Logs and common errors
Events	Handlers for rebuilds, saves, selections, document switches
Script buttons and UI	Script folder, buttons, startup scripts, progress (Esc cancels), dialogs
Building models	Sketches, features, assemblies and mates, drawings, export
API reference	Every public class and function

Every runnable example in the guide is executed against SOLIDWORKS by the test suite.

How it works

SOLIDWORKS (SLDWORKS.exe, .NET Framework 4.8)
 └─ SwPy.AddIn (C#)  ── task pane IDE (WinForms + Scintilla)
     │                └─ COM entry point Execute(session, code)  ◄── swpy.client / Excel / C#
     └─ pythonnet ──► CPython 3.12 (bundled)
                        ├─ swpy._host     sessions, output, errors, # r: packages
                        ├─ swpy._editor   completion, signatures, hover, syntax check
                        ├─ swpy.com       auto-typed COM proxies
                        └─ swpy.model     Pythonic layer (units, dims, globals, queries)

Design notes and research findings: docs/ARCHITECTURE.md and docs/RESEARCH.md.

Project structure

├── src/
│   ├── SwPy.AddIn/          C# add-in: COM registration, Python host, task-pane IDE (Ui/)
│   └── SwPy.Launcher/       starts SOLIDWORKS and loads the add-in (per-user installs)
├── python/swpy/             the Python package (runs inside SOLIDWORKS; client.py runs anywhere)
├── tests/                   live pytest suite (drives a real SOLIDWORKS)
├── tools/                   install/register scripts, runtime fetcher, interop generator
├── docs/
│   ├── guide/               user guide and API reference
│   ├── ARCHITECTURE.md      layers and milestones
│   └── RESEARCH.md          findings that shaped the design
├── pyproject.toml           package metadata (editable install for the client / dev tools)
├── CHANGELOG.md
├── CONTRIBUTING.md
└── LICENSE

Development

py -3.12 -m venv .venv; .venv\Scripts\pip install -e .[dev]
powershell tools\fetch_python.ps1                # bundle the embeddable runtime (optional for dev)
dotnet build src\SwPy.AddIn -c Debug             # SOLIDWORKS must be closed (DLL lock)
dotnet build src\SwPy.Launcher -c Debug
powershell tools\register.ps1                    # per-user COM registration of the Debug build
.venv\Scripts\python -m pytest tests -q          # starts SOLIDWORKS, loads the add-in, runs the suite

Release package: powershell tools\package.ps1 builds dist\SwPy-<version>.zip. See CONTRIBUTING.md for the test layout, the dev loop (reloading Python without restarting SOLIDWORKS), conventions and release builds. Logs: %LOCALAPPDATA%\SwPy\logs\swpy.log.

Security

SwPy runs scripts with your Windows permissions inside SOLIDWORKS - treat scripts like macros and only run code you trust. See SECURITY.md for the trust model and how to report a vulnerability.

Changelog

See CHANGELOG.md.

License

MIT © 2026 muerus. SOLIDWORKS is a registered trademark of Dassault Systèmes SolidWorks Corporation. This project is not affiliated with or endorsed by Dassault Systèmes.