Sum each matrix column

Return column totals for a rectangular matrix.

vectors arrays numpy-style

Implement `column_sums(matrix: list[list[float]]) -> list[float]`.

Constraints: Pure Python lists only (no numpy import required in browser).

Constraints

Pure Python lists only (no numpy import required in browser).

Example

>>> column_sums(...)
# see tests

10 points ~12 min

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Hints

Think element-wise across aligned indices.

Handle empty inputs before loops.

Test Results

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