Deterministic operators

Transform

Derive fields from every row with deterministic Python.

Transform maps each distinct input value to fields produced by a trusted callable. It is the right choice for parsing, arithmetic, normalization, and other exact row-local work.

Worked example

Transform(
    name="parse-published-time",
    input_spaces=("headlines",),
    output_space="parsed-headlines",
    primary_key="news_id",
    evidence=("published_at_raw",),
    fn=PythonFunction(
        name="parse_published_time",
        source="""from datetime import datetime
def parse_published_time(row):
    try:
        value = datetime.fromisoformat(row["published_at_raw"])
    except (TypeError, ValueError):
        value = None
    return {
        "published_at": value
    }
""",
    ),
    emits=("published_at",),
)

Callable contract

fn(row) -> mapping. The returned fields are added to the source row.

Rows available to the callable

Each row argument contains the declared primary-key fields and the declared evidence fields available for that input role. If the callable reads a field that is not part of the primary key, declare it as evidence.

Parameter	Default	Meaning
`input_spaces`	required	The Space or Spaces read by the task.
`output_space`	required	The Space that receives the task output.
`name`	required	A stable task name used in sessions, reviews, and metrics.
`primary_key`	id	The field, or tuple of fields, that identifies one task input. Duplicate primary-key values are evaluated once.
`evidence`	none	Optional fields made available to the callable in addition to the primary key.
`fn`	required	A deterministic callable that completely defines the operation's decision. Use an importable named function from your package, or PythonFunction(name=..., source=...) when authoring through the hosted API or node editor. Pairwise endomorphic functions may declare an exact indexed candidate_gate.
`function_parameters`	registered defaults	Typed values bound to parameters declared by the registered function. Finite candidate sets let reviewed evidence support parameter advice.

Parameter	Default	Meaning
`emits`	none	Descriptive names of fields produced by the callable.

Output

One output row per distinct primary-key value, with produced fields attached.

Design guidance

Prefer Transform over SemTransform whenever the result can be computed reliably. This avoids model cost and makes the output exactly reproducible. A hosted PythonFunction may catch ValueError, TypeError, or OverflowError around parsing; broad exception handlers, raise, else, and finally are not accepted.