(Python)

The four compass points can be abbreviated by single-letter strings as N, E, S, and W. Write a function turn_clockwise that takes one of these four compass points as its parameter, and returns the next compass point in the clockwise direction. Here are some tests that should pass:

test(turn_clockwise("N") == "E")

test(turn_clockwise("W") == "N")

You might ask What if the argument to the function is some other value? For all other cases, the function should return the value

None:

test(turn_clockwise(42) == None)

test(turn_clockwise("rubbish") == None)