bindings

a320-sim — PyO3 bindings

Python extension exposing the headless A320 systems core (a320-sim-core, which vendors and links FlyByWire's Rust systems crates) as a synchronous Sim class.

Only trivial types cross the FFI boundary — f64 / bool / str / list / dict. No FBW types leak into Python. Typed core errors (ApiError) surface as Python exceptions, never panics.

Requirements

Building this package needs both toolchains, because it compiles the Rust core (and the vendored FBW monorepo) into a Python extension:

• Rust 1.93.0 — auto-installs from rust-toolchain.toml on first build. On Windows this is the MSVC target (Visual Studio C++ Build Tools).
• Python ≥ 3.9 with pip.
• The FBW submodule must be checked out first (core-rs/vendor/aircraft), e.g. via scripts\bootstrap-vendor.ps1 from the repo root.

Build (editable install)

From this bindings/ directory, in a clean virtual environment:

python -m venv .venv
.\.venv\Scripts\Activate.ps1      # Linux/macOS: source .venv/bin/activate
pip install -e .

(pip pulls maturin in automatically via build isolation, per pyproject.toml; installing it yourself is only needed for maturin develop.)

The first build compiles the whole FBW dependency graph and takes several minutes. After it finishes:

import a320_sim

sim = a320_sim.Sim()                 # cold & dark on the apron
sim.set("OVHD_ELEC_BAT_1_PB_IS_AUTO", 1)
sim.set("OVHD_ELEC_BAT_2_PB_IS_AUTO", 1)
sim.run(2.0, 5.0)                    # settle ~2 s at 5 Hz
print(sim.get(["ELEC_DC_BAT_BUS_IS_POWERED"]))   # -> {'ELEC_DC_BAT_BUS_IS_POWERED': 1.0}

maturin develop (from an activated venv) is the fast iteration alternative to pip install -e . and produces the same importable module.

API

Sim() mirrors the core api::Sim contract 1:1:

Method	Signature	Notes
set	set(control: str, value: float) -> None	True/1 accepted; raises UnknownControlError / BadValueError
get	get(vars: list[str]) -> dict[str, float]	raises UnknownControlError on an unknown name
step	step(dt_ms: int) -> None	one tick
run	run(seconds: float, rate: float) -> None	ticks at rate Hz
set_environment	set_environment(altitude_ft, indicated_airspeed_kt, oat_celsius, qnh_hpa) -> None	the outside world
snapshot	snapshot() -> dict[str, float]	every known variable
list_variables	list_variables() -> list[str]	discovery
sim_time	sim_time() -> float	monotonic seconds

Exceptions: SimError (base), UnknownControlError, BadValueError.

read_ecam() and failure injection (Phase 2) and list_controls() (issue #12) are added when they exist in the core; they are intentionally not stubbed here.

Tests

cargo test                                   # native: compiles the crate + core
python tests\test_smoke.py                   # Python smoke test (no pytest needed)

License

GPL-3.0-or-later — inherited from the linked FlyByWire crates.