pybFoam

Python bindings for OpenFOAM - enabling direct manipulation of OpenFOAM cases, fields, and meshes from Python.

Documentation — tutorials, how-to guides (generated from runnable examples), API reference, and design notes.

Build the docs locally:

uv sync --extra docs
cd docs && uv run make html
# open docs/_build/html/index.html

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Features

• Direct Python access to OpenFOAM data structures: Time, fvMesh, fields
• Finite volume operators: fvc (calculus), fvm (matrix operations)
• Turbulence and thermodynamic models: Access to OpenFOAM turbulence and thermo libraries
• Sampling and post-processing: Surface sampling, line sampling, interpolation
• Pydantic configuration models: Type-safe dictionary construction for sampling surfaces
• NumPy integration: Zero-copy access to OpenFOAM field data via buffer protocol

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Requirements

• OpenFOAM: v2312 or higher (sourced and installed)
• Python: 3.9 or higher
• CMake: 3.18 or higher
• C++ Compiler: C++17 compatible (GCC 7+, Clang 5+)
• Build tools: nanobind, scikit-build-core
• Build tools: ninja
• Python packages: numpy, pydantic

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Installation

Prerequisites

1. Source your OpenFOAM environment:

   source /path/to/OpenFOAM/etc/bashrc

2. (Recommended) Create a virtual environment:

   python -m venv .venv
   source .venv/bin/activate

Install from source

CC="$(wmake -show-path-c)" CXX="$(wmake -show-path-cxx)" pip install .

For development:

CC="$(wmake -show-path-c)" CXX="$(wmake -show-path-cxx)" pip install -e .[all]

Generating Type Stubs (Development only)

Type stubs (.pyi files) are generated post-installation using a separate script:

# Install the package first
uv pip install -e .[all]

# Generate and verify stubs
./scripts/generate_stubs.sh

This script:

1. Generates stubs using pybind11-stubgen
2. Cleans and formats the stubs
3. Copies them to the source directory
4. Verifies them with mypy

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Quick Start

Basic Usage

import pybFoam as pf

# Create OpenFOAM time and mesh
time = pf.Time(".", ".")
mesh = pf.fvMesh(time)

# Access fields
p_rgh = pf.volScalarField.read_field(mesh, "p_rgh")
U = pf.volVectorField.read_field(mesh, "U")

# Compute gradients using finite volume calculus
grad_p = pf.fvc.grad(p_rgh)
div_U = pf.fvc.div(U)

# Convert to NumPy arrays for analysis
import numpy as np
p_array = np.asarray(p_rgh["internalField"])
print(f"Pressure range: {p_array.min():.3f} to {p_array.max():.3f}")

Sampling Surfaces

from pybFoam.sampling import SampledPlaneConfig, sampledSurface, interpolationScalar
from pybFoam import Word

# Create a sampling plane using Pydantic config
plane_config = SampledPlaneConfig(
    point=[0.5, 0.5, 0.0],
    normal=[1.0, 0.0, 0.0]
)

# Create the surface
plane = sampledSurface.New(Word("myPlane"), mesh, plane_config.to_foam_dict())
plane.update()

# Interpolate field onto surface
interp = interpolationScalar.New(Word("cellPoint"), p)
sampled_values = interp.sampleOnFaces(plane)

Read OpenFOAM dictionaries

from pybFoam import Word, dictionary

d = dictionary.read("system/controlDict")

# Typed accessors — a typo in the key raises at the call site
application = d.get[Word]("application")
end_time    = d.get[float]("endTime")
max_co      = d.getOrDefault[float]("maxCo", 0.5)

# Nested subdictionaries and key enumeration
piso = d.subDict("PISO")
for name in d.toc():
    print(name)

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Examples

Runnable, self-contained scripts live under examples/. They are executed at documentation build time and rendered as the tutorials and how-to guides on the docs site.

• Tutorials (examples/tutorials/) — end-to-end walkthroughs that build on each other:
  • example_01_getting_started.py — open a case, read a field, NumPy view
  • example_02_field_analysis.py — drive a time loop and summarise per-step statistics
  • example_03_sampling_workflow.py — sample a plane, export to CSV
• How-to guides (examples/how-to/) — task-focused recipes:
  • example_read_dictionaries.py — controlDict / typed entries
  • example_blockmesh.py — generate_blockmesh + checkMesh
  • example_fvc_fvm_operators.py — gradient / divergence / Laplacian and implicit matrix terms
  • example_sample_plane.py, example_sample_line.py
• Case data — examples/case/ and examples/cavity/ are read-only baseline cases consumed by the scripts above.
• Solver example — examples/cavity/icoFoam.py (full PISO loop driven from Python).

More tests with additional API usage live under tests/pybind/.

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Testing

Run the test suite:

pytest tests/

Run specific test categories:

pytest tests/pybind/          # C++ binding tests
pytest tests/test_sampling_models.py  # Pydantic config tests

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Development Setup

1. Clone the repository
2. Install development dependencies:

   pip install -e ".[dev]"
   # or build with stubs
   pip install -e .[all] -C cmake.define.ENABLE_PYBFOAM_STUBS=ON -v

3. Run tests before committing:

   pytest tests/

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License

See LICENSE file for details.

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