rohitg00/ai-engineering-from-scratch · error · ValueError

weights length must match rankings length

Error message

weights length must match rankings length

What it means

Error "weights length must match rankings length" thrown in rohitg00/ai-engineering-from-scratch.

Source

Thrown at phases/19-capstone-projects/65-hybrid-retrieval-bm25-dense/code/main.py:151

        qv = mock_embed(query)
        scored = [(d, cosine(qv, v)) for d, v in self.vectors]
        scored.sort(key=lambda x: -x[1])
        return scored[:k]


# ---------------------------------------------------------------------------
# Reciprocal Rank Fusion
# ---------------------------------------------------------------------------

def rrf(
    rankings: list[list[tuple[Doc, float]]],
    k: int = 60,
    weights: list[float] | None = None,
) -> list[tuple[Doc, float]]:
    if weights is None:
        weights = [1.0] * len(rankings)
    if len(weights) != len(rankings):
        raise ValueError("weights length must match rankings length")
    score: dict[str, float] = defaultdict(float)
    by_id: dict[str, Doc] = {}
    for w, ranks in zip(weights, rankings):
        for rank, (doc, _) in enumerate(ranks):
            score[doc.doc_id] += w * (1.0 / (k + rank + 1))
            by_id[doc.doc_id] = doc
    fused = sorted(score.items(), key=lambda x: -x[1])
    return [(by_id[did], s) for did, s in fused]


# ---------------------------------------------------------------------------
# Hybrid retriever
# ---------------------------------------------------------------------------

@dataclass
class HybridRetriever:
    bm25: BM25Index = field(default_factory=BM25Index)
    dense: DenseIndex = field(default_factory=DenseIndex)

View on GitHub (pinned to 39ea8a1c6d)

When it happens

Trigger: Thrown at phases/19-capstone-projects/65-hybrid-retrieval-bm25-dense/code/main.py:151 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of rohitg00/ai-engineering-from-scratch@39ea8a1c6d (2026-08-26). Data as JSON: /api/errors/0d891657c47c4dea. Report an issue: GitHub.