return (radius, angle) of a vector(x, y)

def radang(x, y):
    '''return (radius, angle) of a vector(x, y)'''
    if x == 0:
        if y == 0:
            return 0, 0
        return abs(y), 90+180*(y<0)
    if y == 0:
        return abs(x), 180*(x<0)

    r = math.sqrt(x*x+y*y)
    a = math.degrees(math.atan(y/x))
    if x < 0:
        a += 180
    elif y < 0:
        a += 360
    return r, a