01 · Hello, local Python

The leaf node. If the SDK is not importable or the decorator is broken, nothing above this can be green. Two minutes, no infrastructure.

Exercises

The Python SDK install path (uv / pip / editable).
@dls.udf semantics — a bare @udf (no queue=) runs the decorated function in-process on a direct call.
The always-local escape hatch: train.local(...) bypasses any queue binding, so test code stays stable when the decorator later gains one.

Requires

A Python ≥ 3.11 environment with dreamlake-lakeshore importable.
That is it. No control plane, no daemon, no network — the local tier does not even import httpx or msgpack.

Verifies

The SDK as a leaf node. It imports cleanly, the decorator wraps without error, and the function executes and returns its value verbatim.

Run

bash

cd lakeshore-examples/02-hello-local-python
uv run train.py

train.py carries inline script metadata whose [tool.uv.sources] block pins dreamlake-lakeshore to the ../../lakeshore-py checkout as an editable install — so this runs the local source tree, not PyPI. To exercise the published package instead, delete that block from the script header; the sibling pyproject.toml declares dreamlake-lakeshore>=0.3.7.

Plain pip works too:

bash

pip install -e lakeshore-py     # or: pip install dreamlake-lakeshore
python lakeshore-examples/02-hello-local-python/train.py

Expected output

{'seed': 42, 'loss': 0.6394267984578837}
{'seed': 7, 'loss': 0.32383276483316237}
{'seed': 1, 'loss': 0.13436424411240122}

Three dicts, deterministic across runs because the example seeds random. The third line comes from train.local(seed=1).

If it fails

Symptom	Likely cause
`ModuleNotFoundError: No module named 'dreamlake'`	The SDK is not in the active environment. Use `uv run --with-editable lakeshore-py ...` or `pip install -e lakeshore-py`. Note the install name is `dreamlake-lakeshore`, the import path `dreamlake.lakeshore`.
`TypeError` on the decorator	An SDK version mismatch — the example declares `dreamlake-lakeshore>=0.3.7`. Bump or pin.
Different `loss` values	Check that the example still seeds `random` before each call. The shape is what matters.

Status

loading…

Runs in the example smoke set; refresh /test-results.json via uv run lakeshore-examples/test_runner.py.

→ 02 · Hello, hosted control plane