openbim-ifc (Python)

Read, edit and write IFC STEP files from Python. A thin binding over the openbim-ifc Rust crates: one abi3 wheel for CPython 3.9 and later.

from openbim_ifc import IfcModel, Text

with open("model.ifc", "rb") as f:
    model = IfcModel.parse(f.read())

print(model.schema, len(model))
for id in model.ids_of_type_including_subtypes("IfcWall"):
    print(id, model.attribute(id, 2))      # Name, e.g. Text('Wall')

model.set_attribute(id, 2, Text("Renamed"))
with open("out.ifc", "wb") as f:
    f.write(model.write())

Values

Attribute values are frozen dataclasses, one per STEP form: Null ($), Derived (*), Bool, Unknown (.U.), Integer, Real, Text, Binary, Enum, Ref (#42), List, and Typed (IFCLENGTHMEASURE(2.5)). They keep every distinction IFC makes, so a file read and written back through Python is unchanged.

Bare Python values are refused with TypeError: 3 could be an Integer or a Real, "x" a Text or an Enum, and the binding does not guess.

Errors

Every failure raises IfcError with a stable code: parse, write, missing-entity, invalid-value, out-of-range or unsupported-schema. The codes are shared with the JavaScript and C bindings.

Threads

parse releases the GIL while it reads. A model can be passed between threads; the GIL serialises calls on it.

Scope

The record model only: entities, attributes, the STEP codec, exact and subtype queries. Domain views (properties, quantities, geometry) are not bound yet. The wheel is built and tested in CI; it is not on PyPI yet.

Build

uv venv && . .venv/bin/activate
uv pip install maturin
maturin develop --release     # or: scripts/check-python.sh to build + test

Faster reading (opt-in)

maturin build --release --features mimalloc

Uses the mimalloc allocator for the extension's own memory: reading STEP takes 23-36% fewer CPU cycles, but 2-28% more memory stays resident. Off by default because mimalloc is C code and the project is pure Rust; #49 tracks a pure-Rust replacement.