btap (Python)

The Python port of the btap gem family — one distribution, five subpackages mirroring the gems (btap.audit, btap.simulation, btap.modeling, btap.costing, btap.necb), same one-way dependency direction (D-77). The port is COMPLETE (M0–M8, 2026-08-28; the record is ../PORT_STATUS.md and D-79), verified three ways: every Ruby suite ported, the Leg-C oracle goldens consumed (frozen AND live), and the Leg-B corpus diff holding the Ruby and Python btap-compliance CLIs equivalent at the none, sizing and annual --quick tiers.

Since R3 (D-81) this implementation is primary and canonical, and since the R4 handoff (D-82) it is the only one that changes: Ruby backports have stopped. Behaviour changes land here with a re-frozen scenario baseline in the same PR (verification/scenarios/freeze.py); the frozen suite — not a live Ruby comparison — is the regression net.

cd python && python3 -m unittest discover tests   # stdlib-only, no install needed (serial)
cd python && .venv/bin/pytest -n auto tests/      # parallel (pytest-xdist worker
                                                  # processes; ~10x on the E+ suites)

btap/_compat.py holds the cross-cutting Ruby-parity contracts (round-half- away rounding, SDK Optional unwrapping, the NullAudit, determinism-critical sorting, HTML escaping). New code uses those helpers, never the raw Python equivalents — the differences they paper over are exactly the silent Ruby-vs-Python drifts the census identified.

The CLI (M6)

The umbrella pipeline and its command line are ported:

pip install .                      # installs the btap-compliance console script
btap-compliance model.osm --epw weather.epw          # full 8.4.1.2 determination
python3 -m btap.necb.cli model.osm --simulate none   # no-install equivalent

Same seven exit codes as the Ruby CLI (0 compliant, 1 not compliant, 2 usage, 3 pre-flight, 4 simulation, 5 internal, 6 no determination), and the same refusal to call a --quick week a determination. The Leg-B corpus gate (CLI_B=python bash verification/selftest.sh) diffs this CLI's audit.json/report.json against the Ruby CLI's over the whole corpus — every pair equivalent at the none, sizing, and annual tiers.

Thermal bridging (M7)

NECB 3.1.1.7 runs through py-tbd (native Python, no Ruby subprocess), pinned by commit SHA to its tbd-3.5.2-compat branch — the revision verified against the family's frozen Ruby TBD 3.5.2 / OSut 0.8.2 oracle baseline:

pip install '.[tbd]'

Without it the pipeline still works: thermal_bridging= degrades to the same loud audited 3.1.1.7-not-accounted warning the Ruby gem emits without its tbd gem — never a silent clear-field result.