IME, I've never seen a situation where `x += y` is preferred over `x.extend(y)`, with the bonus that `extend` works in places where `+=` doesn't, like tuples wh

IME, I've never seen a situation where `x += y` is preferred over `x.extend(y)`, with the bonus that `extend` works in places where `+=` doesn't, like tuples where reassignment isn't possible.