What does the “at” (@) symbol do in Python?

Question

I\'m looking at some Python code which used the @ symbol, but I have no idea what it does. I also do not know what to search for as searching Python docs or Goo

Answer 1

In Python 3.5 you can overload @ as an operator. It is named as __matmul__, because it is designed to do matrix multiplication, but it can be anything you want. See PEP465 for details.

This is a simple implementation of matrix multiplication.

class Mat(list):
    def __matmul__(self, B):
        A = self
        return Mat([[sum(A[i][k]*B[k][j] for k in range(len(B)))
                    for j in range(len(B[0])) ] for i in range(len(A))])

A = Mat([[1,3],[7,5]])
B = Mat([[6,8],[4,2]])

print(A @ B)

This code yields:

[[18, 14], [62, 66]]