02-Implement-Our-Own-Matrix

Matrix.py

from .Vector import Vector


class Matrix:

    def __init__(self, list2d):
        self._values = [row[:] for row in list2d]

    def row_vector(self, index):
        """返回矩阵的第index个行向量"""
        return Vector(self._values[index])

    def col_vector(self, index):
        """返回矩阵的第index个列向量"""
        return Vector([row[index] for row in self._values])

    def __getitem__(self, pos):
        """返回矩阵pos位置的元素"""
        r, c = pos
        return self._values[r][c]

    def size(self):
        """返回矩阵的元素个数"""
        r, c = self.shape()
        return r * c

    def row_num(self):
        """返回矩阵的行数"""
        return self.shape()[0]

    __len__ = row_num

    def col_num(self):
        """返回矩阵的列数"""
        return self.shape()[1]

    def shape(self):
        """返回矩阵的形状: (行数， 列数)"""
        return len(self._values), len(self._values[0])

    def __repr__(self):
        return "Matrix({})".format(self._values)

    __str__ = __repr__

main_matrix.py测试

from playLA.Matrix import Matrix


if __name__ == "__main__":

    matrix = Matrix([[1, 2], [3, 4]])
    print(matrix)
    print("matrix.shape = {}".format(matrix.shape()))
    print("matrix.size = {}".format(matrix.size()))
    print("len(matrix) = {}".format(len(matrix)))
    print("matrix[0][0] = {}".format(matrix[0, 0]))

04-Implement-Basic-Operations-of-Matrix

from .Vector import Vector


class Matrix:

    def __init__(self, list2d):
        self._values = [row[:] for row in list2d]

    @classmethod
    def zero(cls, r, c):
        """返回一个r行c列的零矩阵"""
        return cls([[0] * c for _ in range(r)])

    def __add__(self, another):
        """返回两个矩阵的加法结果"""
        assert self.shape() == another.shape(), \
            "Error in adding. Shape of matrix must be same."
        return Matrix([[a + b for a, b in zip(self.row_vector(i), another.row_vector(i))]
                       for i in range(self.row_num())])

    def __sub__(self, another):
        """返回两个矩阵的减法结果"""
        assert self.shape() == another.shape(), \
            "Error in subtracting. Shape of matrix must be same."
        return Matrix([[a - b for a, b in zip(self.row_vector(i), another.row_vector(i))]
                       for i in range(self.row_num())])

    def __mul__(self, k):
        """返回矩阵的数量乘结果: self * k"""
        return Matrix([[e * k for e in self.row_vector(i)]
                       for i in range(self.row_num())])

    def __rmul__(self, k):
        """返回矩阵的数量乘结果: k * self"""
        return self * k

    def __truediv__(self, k):
        """返回数量除法的结果矩阵：self / k"""
        return (1 / k) * self

    def __pos__(self):
        """返回矩阵取正的结果"""
        return 1 * self

    def __neg__(self):
        """返回矩阵取负的结果"""
        return -1 * self

    def row_vector(self, index):
        """返回矩阵的第index个行向量"""
        return Vector(self._values[index])

    def col_vector(self, index):
        """返回矩阵的第index个列向量"""
        return Vector([row[index] for row in self._values])

    def __getitem__(self, pos):
        """返回矩阵pos位置的元素"""
        r, c = pos
        return self._values[r][c]

    def size(self):
        """返回矩阵的元素个数"""
        r, c = self.shape()
        return r * c

    def row_num(self):
        """返回矩阵的行数"""
        return self.shape()[0]

    __len__ = row_num

    def col_num(self):
        """返回矩阵的列数"""
        return self.shape()[1]

    def shape(self):
        """返回矩阵的形状: (行数， 列数)"""
        return len(self._values), len(self._values[0])

    def __repr__(self):
        return "Matrix({})".format(self._values)

    __str__ = __repr__

测试

from playLA.Matrix import Matrix


if __name__ == "__main__":

    matrix = Matrix([[1, 2], [3, 4]])
    print(matrix)
    print("matrix.shape = {}".format(matrix.shape()))
    print("matrix.size = {}".format(matrix.size()))
    print("len(matrix) = {}".format(len(matrix)))
    print("matrix[0][0] = {}".format(matrix[0, 0]))

    matrix2 = Matrix([[5, 6], [7, 8]])
    print(matrix2)
    print("add: {}".format(matrix + matrix2))
    print("subtract: {}".format(matrix - matrix2))
    print("scalar-mul: {}".format(2 * matrix))
    print("scalar-mul: {}".format(matrix * 2))
    print("zero_2_3: {}".format(Matrix.zero(2, 3)))