SysML v2 Python Units

Convert units and quantities between standard SysML v2 and Python with Syside Automator and Pint.

• Get/set quantity* as attribute value, specified using Pint Quantity objects
• Get/set unit as attribute value, specified using Pint Unit objects
• Supports numerical values, as well as inf (* in SysML v2) and NaN (set as null in SysML v2)
• Supports compound units, for example K·kg·s²/m³
• Supports unit prefixes (kilo, mega, milli, etc.)
• Supports percentages
• Derive preferred units for a quantity type, for example kg for an ISQ::mass quantity
• Gracefully handle units that are not supported by SysML v2: stored as doc _units /* <units> */ (opt-in)
• Conversion functions between SysML v2 units and Pint Unit, and string parsing functions
• Syside Automator ReferencePrinter for printing unit references using their short name
• Extensive caching to make units lookup fast

*: a quantity is a combination of a numerical value (the "magnitude") and units, for example: 10 kg, -1.0 m/s**2.

Note: this package uses Syside Automator for parsing SysML v2 models. Syside Automator is commercial software, so you have to obtain a license first. For academic uses you can request an academic license.

Installation

1. Install the package from PyPI:

   pip install sysmlv2-units
   

   Note: currently Syside Automator only supports Python 3.12
2. Make sure you activate Syside Automator

Usage

Refer to the documentation.

Citing

If you use this library in your work, please cite the paper that first introduces the use of these capabilities:

Bussemaker, J.H. et al., 2026, April. System Architecture Optimization Using SysML v2: Language Extension and Implementation. IEEE SysCon 2026, Halifax, Canada. doi: 10.1109/SysCon66367.2026.11503593

Contributing

The project is coordinated by: Jasper Bussemaker (jasper.bussemaker at dlr.de)

If you find a bug or have a feature request, please file an issue using the Github issue tracker. If you require support for using the library or want to collaborate, feel free to contact me.

Contributions are appreciated too:

• Fork the repository
• Add your contributions to the fork
  • Update/add documentation
  • Add tests and make sure they pass (tests are run using pytest)
• Sign a Contributor License Agreement (CLA): please contact me for the template
• Issue a pull request