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# это пример показывает применение __matmul__ и __imatmul__ для пользовательских классов | |
class MyMatrix: | |
def __init__(self, data): | |
self.data = data | |
# для получения элементов матрицы как A[строка, столбец] | |
def __getitem__(self, pos): | |
i, j = pos | |
return self.data[i][j] | |
# реализует оператор @ для нашей MyMatrix | |
def __matmul__(self, B: 'MyMatrix'): | |
A = self | |
b_rows = len(B.data) | |
b_cols = len(B.data[0]) | |
a_rows = len(A.data) | |
data = [[sum(A[i, k] * B[k, j] for k in range(b_rows)) for j in range(b_cols)] for i in range(a_rows)] | |
return MyMatrix(data) | |
# добавим также оператор @= | |
def __imatmul__(self, other): | |
self.data = (self @ other).data | |
return self | |
# для печати | |
def __str__(self): | |
return str(self.data) | |
print('-' * 20, 'MY MATRIX DEMO', '-' * 20) | |
a = MyMatrix([ | |
[1, 2], | |
[3, 4] | |
]) | |
print("a =", a) | |
b = MyMatrix([ | |
[5, 0], | |
[-1, 3] | |
]) | |
print("b =", b) | |
b @= MyMatrix([ | |
[-1, 0], | |
[0, -1] | |
]) | |
print("b @ (-E) =", b) | |
print("a @ b =", a @ b) | |
# проверим правильность через numpy | |
print('-' * 20, 'NUMPY', '-' * 20) | |
import numpy as np | |
a = np.array([ | |
[1, 2], | |
[3, 4] | |
]) | |
print("a =", a.tolist()) | |
b = np.array([ | |
[5, 0], | |
[-1, 3] | |
]) | |
print("b =", b.tolist()) | |
e = np.eye(2, dtype=int) | |
# numpy не поддерживает @= | |
try: | |
b @= -e | |
except TypeError as t: | |
print(t) | |
b = b @ -e | |
print("b @ (-E) =", b.tolist()) | |
print("a @ b =", (a @ b).tolist()) |
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