python-playground

Playground for developing / demonstrating python dev techniques.

This repository hosts Acoustic Reference Book — Phase 1: a schema-driven pipeline that turns acoustic calculation output into validated XML Acoustic Dataset, built as a learning project where every decision is documented and defensible.

Quick start

Open in a GitHub Codespace (Code → Codespaces → Create codespace). It provisions Python 3.9.4 (matching the target system) and runs make bootstrap automatically. Then:

make verify # lint + tests — confirm the environment is green
make docs-serve # browse the docs at http://localhost:8000

Working locally instead? You need Python 3.9.x and make, then make bootstrap. Run make to see all targets.

Self-guided adventures

New here? Work through these in order. Each is a short, hands-on loop — run a command, look at what it produced, then peek at the code that did it. Everything below has been run end-to-end, so the output you see should match.

All commands assume make bootstrap has finished (it runs automatically in a Codespace). If acoustic isn't found, the package is exposed as a module too: replace acoustic with python -m acoustic_dataset.cli.

Adventure 1 — Run the whole pipeline and watch the gates

make verify # lint + type-check + tests: is the env green?
acoustic pipeline # input XML -> typed objects -> XML -> validate

You should see something like:

pipeline ok: 10 band(s) -> build/acoustic_dataset.xml (schema-valid, round-trip-equal)

Open the file it wrote (build/acoustic_dataset.xml) and compare it to the input (examples/calculation_input.xml). Then run the structural gate on its own and the migration-safety diff against the known-good reference:

acoustic validate --xml build/acoustic_dataset.xml
acoustic compare build/acoustic_dataset.xml examples/reference/trial_known_good.xml

Now make it your own.examples/calculation_input.xml is your sandbox — edit a value and re-run to watch the validated output change. Bump <BandCount>10 to 20, or <BaseLevelDb>140.0 to 155.0, then:

acoustic pipeline

The band count in the message and the generated XML move with your edit. This is the tightest loop in the project: input XML in, validated dataset out.

Then break it on purpose to watch the gates earn their keep. Set <BandCount> to a negative number, or put text where a number belongs, and re-run:

error: build rejected a value before serialisation: ... schema: value must be positive

The pipeline rejects it, prints the reason, exits non-zero, and does not write a stale artifact. (Restore the file afterward — git checkout examples/calculation_input.xml.)

Now read why:docs/concepts/two-verification-gates.md explains why "schema-valid" and "correct" are two different checks. The code lives in src/acoustic_dataset/validate.py and compare.py, dispatched from cli.py.

Adventure 2 — Explore a typed Python data class

The pipeline never carries data in a loose dict; it builds one typed object that meets the schema. Feel the difference yourself.

First, experience editor autocomplete. Open examples/explore_platform.py in VS Code (the Codespace ships Pylance). Find the # platform.radiated_noise. line, delete the #, put your cursor right after the dot, and type: VS Code pops up the object's declared attributes (band, …) — statically, before the code has even run. Try platform. too for the top-level attributes (radiated_noise, sensors, …). Keep drilling (platform.radiated_noise.band[0].) and it completes all the way down. That instant, schema-shaped autocomplete is the real payoff of declared fields. Run the file any time with:

python examples/explore_platform.py

If autocomplete doesn't appear, give Pylance a moment to index, and make sure VS Code's Python interpreter is set to the Codespace's 3.9 (bottom-right status bar / Python: Select Interpreter).

Then poke at it in the REPL:

python

>>>fromacoustic_datasetimportbuild, serialize>>>platform=build.build_platform_from_file("examples/calculation_input.xml")
>>>type(platform).__name__'Platform'>>>platform.radiated_noise.band[0].centre_frequency# a Decimal, not a string>>>print(serialize.to_xml(platform)[:500]) # the same object, as XML>>>fromacoustic_dataset.models.acoustic_datasetimportSector>>>Sector(bering=1, level=2) # a typo is a TypeError, not a silent new key

The REPL can also complete attributes, but that's a separate readline/rlcompleter feature that introspects the live object at runtime — not the static, declared-field completion you saw in the editor. If <TAB> doesn't complete, enable it for the session with import readline, rlcompleter; readline.parse_and_bind("tab: complete").

Read docs/concepts/typed-vs-dicts.md for what declared fields buy you over a dictionary, then look at how the builder rejects out-of-range values in src/acoustic_dataset/build.py.

Adventure 3 — Reverse-engineer the data classes from the schema

Those data classes aren't hand-written — they're generated from the XSD by xsdata. The XSD is the single source of truth; the Python is a build artifact (note the # DO NOT EDIT BY HAND header on every model file).

acoustic generate # regenerate models from every schema/*.xsd

Trace the chain for one element:

1. Open schema/acoustic_dataset.xsd and find an element, e.g. Sector.
2. Open the generated src/acoustic_dataset/models/acoustic_dataset.py and find the matching @dataclass. Notice how XSD types, ranges, and docs became Python field metadata.
3. Read src/acoustic_dataset/generate.py to see the exact xsdata invocation — and the two post-processing steps that keep the output deterministic and Python-3.9-compatible.

Want to see generation in action? Change a <xs:documentation> string in the XSD, run acoustic generate, and git diff the models — the docstring tracks the schema. (Revert the XSD edit afterward; CI fails if committed models drift from the schema — ADR 0008.)

Adventure 4 — Generate and view the XSD documentation

Two complementary docs come out of this repo. First, a standalone HTML schema reference rendered straight from the XSD (via the vendored xs3p stylesheet):

acoustic gen-schema-docs --out build/schema-preview.html

Open build/schema-preview.html (in a Codespace: right-click the file → Download, or use the Live Preview extension) to browse every element, type, and constraint of the contract. The pre-built version is committed at docs/reference/schema/index.html. The generator lives in src/acoustic_dataset/schema_html.py.

Second, the full project site — tutorials, concepts, ADRs, and a Mermaid ERD — served by MkDocs Material:

make docs-serve # browse at http://localhost:8000

In a Codespace, when the port-forward notification appears, click Open in Browser.

Adventure 5 — Point it at the real (private) schema

Everything above runs against the placeholder schema committed in schema/. The real, proprietary XSD and corpus are meant to live under private/ — a directory that is entirely gitignored (see .gitignore) so it never reaches git, CI, or the internet.

One constraint shapes the workflow: src/acoustic_dataset/models/ is committed (the placeholder-generated models that CI drift-checks), so you must not regenerate over it from a real schema — an accidental commit would leak that structure. Generate real models into private/ instead. The same CLI takes explicit paths, so once the real material is in place (real XSD in private/schema/, inputs in private/examples/, known-good XML in private/reference/):

# Generate typed models from the real XSD into the gitignored output dir
acoustic generate --schema private/schema/<real>.xsd --out private/models
# Structural gate (XSD + round-trip) on a real file against the real schema
acoustic validate --xml private/examples/<real>.xml --schema private/schema/<real>.xsd
# Migration-safety diff: generated vs known-good reference
acoustic compare private/<generated>.xml private/reference/<known_good>.xml

Caveat — the full pipeline command.acoustic pipeline imports acoustic_dataset.models (the committed package), so it always builds against the placeholder-derived bindings even when you pass --schema private/.... Running the end-to-end pipeline on real-generated models would mean repointing that import at private/models/ — a deliberate change that touches committed code, so raise it for review first. With the real schema you can use generate, validate, and compare against private/ paths immediately; full pipeline needs that reviewed change.

Where to go next

Follow the guided tutorial that ties all of this together: docs/tutorials/01-start-here.md, then skim the decision records in docs/decisions/ — each says why a choice was made and what was rejected.

Documentation

The full, navigable documentation — tutorials, how-to guides, concepts, decision records (ADRs), and a Mermaid schema ERD — lives in docs/ and renders as an attractive HTML site via MkDocs Material (make docs).

Start here:docs/tutorials/01-start-here.md.

Spec-driven development

This project uses GitHub Spec Kit. The active feature's specification, plan, and design artifacts are under specs/001-codespace-xml-scaffold/. Use the /speckit-* skills (specify, plan, tasks, implement) to drive development.

Layout

Path	What it is
.devcontainer/	Codespaces environment (Python 3.9.4)
schema/	The XSD contract
src/acoustic_dataset/	The pipeline package (models/ is generated, never hand-edited)
examples/	Example calculation input + reference/ known-good files
tests/	Unit, integration, and golden-file tests
docs/	The documentation site (MkDocs Material)
specs/	Spec Kit feature specs, plans, and contracts