Python怎么判断点在直线上方还是下方，给我个代码示例

可以使用向量叉积的方式判断点在直线上方还是下方，代码示例如下：

class Point:
    def __init__(self, x, y):
        self.x = x
        self.y = y

class Line:
    def __init__(self, p1, p2):
        self.p1 = p1
        self.p2 = p2

def cross_product(p1, p2):
    return p1.x * p2.y - p2.x * p1.y

def point_above_or_below_line(point, line):
    vector1 = Point(line.p2.x - line.p1.x, line.p2.y - line.p1.y)
    vector2 = Point(point.x - line.p1.x, point.y - line.p1.y)
    cross = cross_product(vector1, vector2)
    if cross > 0:
        return "above"
    elif cross < 0:
        return "below"
    else:
        return "on the line"

# 示例
p1 = Point(1, 1)
p2 = Point(2, 2)
line = Line(p1, p2)
point = Point(3, 1)
print(point_above_or_below_line(point, line))  # 输出 "below"

这个示例中，我们定义了一个 `Point` 类表示点，一个 `Line` 类表示直线，使用叉积判断点在直线上方还是下方，返回结果为 "above" 或 "below" 或 "on the line"。