PEP 465 introduced the infix operator @: https://www.python.org/dev/peps/pep-0465/

Python 3.5 was the first version of python3 to implement the PEP: https://docs.python.org/3.5/whatsnew/3.5.html

If I am reading the release notes correctly, Python 3.5.0 was released last year (2015-09-13): https://www.python.org/downloads/release/python-350/

It's fair to say that this is a relatively new development.

It's true that infix multiply is new, but infix multiply if I'm not mistaken is not a breaking change.

True.

I mean in the context as @sampo described it above ...

In the Stanford/Coursera machine learning class, Andrew Ng said that his teaching experience is that students pick up octave/matlab quicker and the course can cover more actual machine learning, compared to python where more time is spent learning the language.

Then "which version of Python, and how is that different..." etc.