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")

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

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.
• Custom properties as a dictionary: model.props["PartNo"] = "P-100", typed values, links, per configuration.
• 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.

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.

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

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

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

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)

├── 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
├── pyproject.toml           package metadata (editable install for the client / dev tools)
├── CHANGELOG.md
├── CONTRIBUTING.md
└── LICENSE

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.

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.

See CHANGELOG.md.

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