> What JS/Ruby/Lisp/Perl/Java do is irrelevant. Hey, C/Go/D/C++ would all be more likely to append by value, but neither of us care a whit because it's asking about Python, which I know nothing about.

I guess my point was that you should be able to infer that Python would be more likely to behave like JS/Ruby/Lisp/Perl/Java than C/Go/D/C++. If you know or can tell by looking at it that it's much more in the first camp then the second, then you should be able to guess. You're probably right that I overstated how easy that is to tell just from the syntax if you don't know anything at all about Python, but it's also pretty short of memorizing implementation details.

> Finally: JS doesn't have matrix as a base type (boolean/number/string/null/undefined/symbol is it, baby), so for this same question, I'd strongly argue that you're simply wrong about bucketing JS with those other languages. Again, for JS the question would revolve around the implementation details of the matrix object and its prototype.

The 'matrix' in the question wasn't a special matrix type, it was just a list of lists. Word-for-word translated into Javascript it would look like:

    let matrix = []
    let row = [0, 0]
    for (let i = 0; i < 2; ++i) matrix.push(row)
    matrix[1][1] = 1