PyMCNP

PyMCNP supports running Monte Carlo N-Particle (MCNP) simulations. It parses MCNP files, enabling automation such as parameter scans, creates MCNP geometry visualization using pyvista. PyMCNP provides a Python API for MCNP input and output files and a command line interface for interacting with MCNP and MCNP files.

Find more information on ReadTheDocs.

Installation

PyMCNP is available on PyPI and can be “pip installed”:

pip install pymcnp

PyMCNP supports Python 3.11 to 3.14.

As of 2026-10-14, PyMCNP doe snot support Python 3.15 since PyMCNP dependency vtk via pyvista does not support Python 3.15.

Automation with AI Coding Agents

PyMCNP ships a skill file, SKILL.md, that describes the API, the parsing contract, and the common pitfalls to an AI coding agent such as Claude Code. With the skill installed (for Claude Code, copy it to ~/.claude/skills/pymcnp/SKILL.md), an agent can write, scan, run, and plot MCNP models for you from a short description, so automating MCNP becomes easy even for complex geometries. The example on ReadTheDocs, 441 iron discs over a rough concrete floor with a flux plot, was created this way from a short prompt. Always review generated models and results before relying on them.

Contributing

PyMCNP welcomes contributions, including issues, pull requests, and MCNP files that PyMCNP fails to parse or visualize.

For more information, see the CONTRIBUTING.md file.

Copyright and License

For copyright and license information, see the COPYRIGHT.md and LICENSE.md files.