def _update(self, frame_no):
        # Helper functions to map various time elements
        def _hour_pos(t):
            return (t.tm_hour + t.tm_min / 60) * pi / 6

        def _min_pos(t):
            return t.tm_min * pi / 30

        def _sec_pos(t):
            return t.tm_sec * pi / 30

        # Clear old hands
        if self._old_time is not None:
            ot = self._old_time
            self._screen.move(self._x, self._y)
            self._screen.draw(self._x + (self._r * sin(_hour_pos(ot))),
                              self._y - (self._r * cos(_hour_pos(ot)) / 2),
                              char=" ", bg=self._bg)
            self._screen.move(self._x, self._y)
            self._screen.draw(self._x + (self._r * sin(_min_pos(ot)) * 2),
                              (self._r * cos(_min_pos(ot))) - self._y,
                              char=" ", bg=self._bg)
            self._screen.move(self._x, self._y)
            self._screen.draw(self._x + (self._r * sin(_sec_pos(ot)) * 2),
                              self._y - (self._r * cos(_sec_pos(ot))),
                              char=" ", bg=self._bg)

        # Draw new ones
        new_time = datetime.datetime.now().timetuple()
        self._screen.move(self._x, self._y)
        self._screen.draw(self._x + (self._r * sin(_hour_pos(new_time))),
                          self._y - (self._r * cos(_hour_pos(new_time)) / 2),
                          colour=Screen.COLOUR_WHITE, bg=self._bg)
        self._screen.move(self._x, self._y)
        self._screen.draw(self._x + (self._r * sin(_min_pos(new_time)) * 2),
                          self._y - (self._r * cos(_min_pos(new_time))),
                          colour=Screen.COLOUR_WHITE, bg=self._bg)
        self._screen.move(self._x, self._y)
        self._screen.draw(self._x + (self._r * sin(_sec_pos(new_time)) * 2),
                          self._y - (self._r * cos(_sec_pos(new_time))),
                          colour=Screen.COLOUR_CYAN, bg=self._bg, thin=True)
        self._screen.print_at("o", self._x, self._y, Screen.COLOUR_YELLOW,
                              Screen.A_BOLD, bg=self._bg)
        self._old_time = new_time
dataset/ETHPy150Open peterbrittain/asciimatics/asciimatics/effects.py/Clock._update/swapped operands of `-`