Sample Weighting

Task

Implement weighted_mean(losses: list[float], sample_weights: list[float]) -> float. Compute the sample-weighted mean of a sequence of per-example losses.

Requirements

• losses and sample_weights have equal length, and every sample weight is non-negative.
• Multiply each loss by its corresponding sample weight and sum the products.
• Divide the weighted sum by the sum of the sample weights, not by the number of examples.
• Return 0.0 when the inputs are empty or the total sample weight is zero.
• Zero-weight examples must have no effect on the result.
• Do not mutate either input.

Example

weighted_mean([0.2, 0.8, 1.4], [2.0, 1.0, 0.0])
# 0.4