134 lines
3.4 KiB
Python
134 lines
3.4 KiB
Python
"""Compute module providing matrix multiplication functionality.
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This module defines a single public function :func:`matmul`, which performs
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standard matrix multiplication for two 2‑D lists.
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The function explicitly checks that the number of columns of the first matrix
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matches the number of rows of the second matrix. If they are mismatched the
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function prints ``"Matrices not compatible :("`` and returns an empty list.
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All variables are named distinctly to aid readability and to avoid
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conflicts.
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"""
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__all__: list[str] = ["matmul", "transpose"]
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import math
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def matmul(
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matrix_a: list[list[float]],
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matrix_b: list[list[float]],
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) -> list[list[float]]:
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"""Return the product of two matrices.
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Parameters
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----------
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matrix_a: list[list[float]]
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The left‑hand operand, a 2‑D list where each inner list represents a row.
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matrix_b: list[list[float]]
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The right‑hand operand, also a 2‑D list.
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Returns
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-------
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list[list[float]]
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The resulting matrix as a 2‑D list. If the matrices cannot be
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multiplied due to incompatible dimensions, an empty list is returned.
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Examples
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--------
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# >>> matmul([[1, 2], [3, 4]], [[5, 6], [7, 8]])
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[[19.0, 22.0], [43.0, 50.0]]
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"""
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if not matrix_a or not matrix_b:
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print("Matrices not compatible :(")
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return []
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rows_a: int = len(matrix_a)
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cols_a: int = len(matrix_a[0])
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rows_b: int = len(matrix_b)
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cols_b: int = len(matrix_b[0])
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if cols_a != rows_b:
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print("Matrices not compatible :(")
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return []
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# Initialise result matrix with zeros
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result: list[list[float]] = [[0.0 for _ in range(cols_b)] for _ in range(rows_a)]
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for i in range(rows_a):
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for j in range(cols_b):
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sum_val: float = 0.0
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for k in range(cols_a):
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sum_val += matrix_a[i][k] * matrix_b[k][j]
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result[i][j] = sum_val
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return result
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def get_rotate(matrix: list[list[float]], angle:int) -> list[list[float]]:
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"""Apply a rotation matrix to a base matrix.
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Parameters
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----------
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matrix: list[list[float]]
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The matrix to be rotated.
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angle: int
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The angle to be rotated.
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Returns
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-------
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list[list[float]]
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Result of *matrix* rotated by *angle*.
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"""
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rows: int = len(matrix)
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cols: int = len(matrix[0])
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if cols != 1:
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print("Can't rotate this matrix! Wrong amount of columns!")
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return [[0, 0],[0, 0]]
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if rows == 2:
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return [[math.cos(angle), -math.sin(angle)], [math.sin(angle), math.cos(angle)]]
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else:
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print("Can't rotate this matrix! Wrong amount of rows!")
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return [[0, 0],[0, 0]]
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return matmul(rotate_matrix, matrix)
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def transpose(matrix: list[list[float]]) -> list[list[float]]:
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"""Return the transpose of a 2‑D list.
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Parameters
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----------
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matrix: list[list[float]]
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The matrix to transpose.
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Returns
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-------
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list[list[float]]
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Transposed matrix.
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"""
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if not matrix:
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return []
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rows = len(matrix)
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cols = len(matrix[0])
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result: list[list[float]] = [[None for _ in range(rows)] for _ in range(cols)]
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for i in range(rows):
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for j in range(cols):
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result[j][i] = matrix[i][j]
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return result
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if __name__ == "__main__":
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print(matmul([[1, 2], [3, 4]], [[5, 6], [7, 8]]))
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print(transpose([[1, 2], [3, 4]]))
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print(len([[1],[0]])) |