you god damn right

sum() accepts any iterable so it's not necessary (and actually slower) to materialise the list before passing it to sum. You can leave out the square brackets in which case this will work like a generator expression and pass individual values to sum as sum requests them.

Check out my solution too, Gracias

Not bad, nice

Great job! Thanks)

o means row, because OP doesn't want to use more than one letter per variable.

i dont get where the 'o' is coming from
Could you explain?

It's been a long time since I worked on this kata (I'm not even sure where the copying by value is taking place anymore although I would assume that it's the array parameter being passed to the determinant function recursively), but my solution looks like it calculates the determinant without copying any values (and certainly not creating entire temporary arrays).

really?what's the alternative method?

This solution has high readability but requires copying matrix elements by value way more than necessary.