Contributing Python Functions¶

Derived-variable modules live in:

python/src/compehndly/derived_variables/

Each function should provide:

1. An eager kernel that operates on polars.Series.
2. A lazy expression builder that operates on polars.Expr.
3. A DerivedFunctionSpec registration.

Single Function Module¶

from compehndly.polars.kernels import DerivedFunctionSpec


def my_kernel(measured: pl.Series, factor: float) -> pl.Series:
    return measured * factor


def my_expr(measured: pl.Expr, factor: float) -> pl.Expr:
    return measured * factor


FUNCTION_SPEC = DerivedFunctionSpec(
    name="my_function",
    kernel=my_kernel,
    expr_builder=my_expr,
)

Multiple Functions In One Module¶

FUNCTION_SPECS = [
    DerivedFunctionSpec(
        name="first_function",
        kernel=first_kernel,
        expr_builder=first_expr,
    ),
    DerivedFunctionSpec(
        name="second_function",
        kernel=second_kernel,
        expr_builder=second_expr,
    ),
]

The public registry is discovered automatically; there is no central registry file to edit.

Tests¶

Add focused unit tests under:

python/tests/derived_variables/

If behavior should be shared across languages, add a case to:

shared/conformance/derived_variables_cases.json

If a function has a stable config-driven entrypoint, add an integration test in:

python/tests/test_polars_integration.py