my_array = np.array([80.6, 120.8, -115.6, -76.1, 131.3, 105.1, 138.4, -81.3,
    -95.3, 89.2, -154.1, 121.4, -85.1, 96.8, 68.2])
(my_array[:-1] * my_array[1:] < 0).sum()
Python code for counting number of zero crossings in an array