Freedom251 › Physics Simulation Software
MontePy
What MontePy is
MontePy is a free Python library for reading, editing, and writing MCNP input files. Its object-oriented interface links related objects such as cells and materials, so changing one object can update references elsewhere. The library supports automating MCNP deck updates, model parameterization, and conversion for other Monte Carlo codes. Documented applications include reactor reconfiguration, fuel shuffling, model parameter studies, and incorporating results from other codes. Installation is available through pip or conda, and browser or local Jupyter notebooks are provided. MontePy primarily targets MCNP 6.2; MCNP 6.3 support is incomplete, and earlier versions may have issues. It handles almost all MCNP input syntax but excludes macrobody facets and other documented limitations. It does not run MCNP or parse output files. Written files generally retain original formatting, although modified objects may be reformatted. The project uses an MIT license.
Who it suits
It suits Python users editing MCNP inputs for reactor studies, fuel work, parameter studies, or model conversion. It is intended for workflows that need file manipulation rather than MCNP execution or output parsing.
What it does well
- Free MIT-licensed Python library
- Object links update references
- pip and conda installation
- Jupyter browser notebooks
- Automates model parameterization
What to know first
- MCNP 6.3 support incomplete
- Earlier MCNP versions may have issues
- Does not run MCNP
- Does not parse output files
Plans
| Plan | Billed and limits | Price |
|---|---|---|
| MontePy | Free Python library; no paid plans stated | Free |
As montepy.org lists them, read 8 Oct 2026. The maker's own page has the final word.
Verdict
MontePy provides programmable MCNP input-file editing without a paid plan. Its strongest fit is automation around supported input syntax; users still need separate tools to run MCNP and analyze outputs.
Facts from MontePy's own pages
- Assessment tools
- No · montepy.org, 24 Sept 2026
- Authoring tools
- No · montepy.org, 24 Sept 2026
- Automation
- Its object-oriented interface supports automating tasks such as updating MCNP decks, parameterizing models, and converting models to other Monte Carlo codes. · montepy.org, 8 Oct 2026
- Browser demos
- The documentation provides Jupyter notebooks that can run in a browser, and says they can also be installed and run locally. · montepy.org, 8 Oct 2026
- Data export
- No · montepy.org, 24 Sept 2026
- Delivery mode
- hybrid · montepy.org, 24 Sept 2026
- Does not run MCNP
- MontePy does not run MCNP or parse MCNP output files. · montepy.org, 8 Oct 2026
- Formatting
- When writing files, MontePy attempts to preserve the original formatting, though modified objects may be reformatted slightly. · montepy.org, 8 Oct 2026
- Free plan
- Yes · montepy.org, 24 Sept 2026
- Input coverage
- The project says it handles almost all MCNP input syntax, but does not support macrobody facets and documents other syntax limitations. · github.com, 8 Oct 2026
- Installation
- The library can be installed with pip or conda. · montepy.org, 8 Oct 2026
- Intended users
- Documented use cases include reactor reconfiguration, fuel shuffling, model parameter studies, and updating models with results from other codes. · montepy.org, 8 Oct 2026
- Lesson library
- No · montepy.org, 24 Sept 2026
- License
- The project’s GitHub repository identifies its license as MIT. · github.com, 8 Oct 2026
- Maker
- The documentation copyright is attributed to Battelle Energy Alliance LLC. · montepy.org, 8 Oct 2026
- Purpose
- MontePy is a Python library for reading, editing, and writing MCNP input files. · montepy.org, 8 Oct 2026
- Semantic model
- MontePy links related input objects, such as cells and materials, so changing an object can update references in the file. · montepy.org, 8 Oct 2026
- Support
- The project directs users to open GitHub issues for feature requests and lists an email address for questions. · github.com, 8 Oct 2026
- Supported MCNP versions
- MontePy primarily supports MCNP 6.2; MCNP 6.3 is not fully supported, and earlier versions may have issues. · montepy.org, 8 Oct 2026
- 3D visuals
- No · montepy.org, 24 Sept 2026
Where MontePy stands on Freedom251
- Physics Simulation Software#33 of 89