Is there really an @ operator in Python to calculate dot product?

Question

Is this answer correct: https://stackoverflow.com/a/39662710/1175080 ?

Quoting that answer.

In Python 3.5, there is a new operator for the dot product, so you can write a= A @ B instead of a= numpy.dot(A,B)

It does not seem to work for me.

$ python3
Python 3.6.1 (default, Apr  4 2017, 09:40:21) 
[GCC 4.2.1 Compatible Apple LLVM 8.1.0 (clang-802.0.38)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> a = [1, 2, 3]
>>> b = [4, 5, 6]
>>> a @ b
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for @: 'list' and 'list'
>>>

But the linked answer has received 6 upvotes, so I must be missing something. Can you provide a complete example that shows how to use the @ operator to calculate a dot product?

Answer 1

See what's new in Python 3.5, section matrix mult (PEP 465):

PEP 465 adds the @ infix operator for matrix multiplication. Currently, no builtin Python types implement the new operator, however, it can be implemented by defining __matmul__(), __rmatmul__(), and __imatmul__() for regular, reflected, and in-place matrix multiplication. The semantics of these methods is similar to that of methods defining other infix arithmetic operators.

So, you would have to implement those methods yourself.

Or, use numpy>=1.10 which already has support for the new operator:

>>> import numpy
>>> x = numpy.ones(3)
>>> m = numpy.eye(3)
>>> x @ m
array([ 1., 1., 1.])