gistfile1.py

def interpolate_angle(a, b, alpha):
    a, b = math.radians(a), math.radians(b)

    # add up weighted unit vectors
    vx = math.cos(a) * (1 - alpha) + math.cos(b) * alpha
    vy = math.sin(a) * (1 - alpha) + math.sin(b) * alpha
    
    # is our unit vector undefined? then return counter-clockwise increasing rotation
    if vx == 0 and vy == 0:
        return (math.degrees(a) + 180 * alpha) % 360
        
    # calculate angle
    return math.degrees(math.atan2(vy, vx)) % 360