Pythons don’t strangle their prey - that is, they do not attempt to compress the trachea by wrapping around the prey’s neck. Instead, they wrap around the thorax and abdomen so as to prevent the lungs from expanding and drawing in air (they may also squeeze hard enough to cause cardiac arrest).
Having said that, it’s not even that specific. It’s more like “wrap as many coils as possible around the prey and squeeze until they stop moving.”
If you already have knife in hand, your arm doesn’t need to be particularly free. As long as you can move his hand and poke a hole or two anywhere in the snake’s body, I expect the snake will start moving around - at which point you can poke more holes in the snake, make it bleed/move more. At some point your arm is freed up enough to really go to work on the snake.
Victory to the biped.