将几何区域系统的实现（ 9.4节）重写为恰当的模块

好的，这是重写后的代码：

import math

class Point:
    def __init__(self, x=0, y=0):
        self.x = x
        self.y = y

    def distance(self, other):
        return math.sqrt((self.x - other.x) ** 2 + (self.y - other.y) ** 2)

class Rectangle:
    def __init__(self, posn, w, h):
        self.corner = posn
        self.width = w
        self.height = h

    def area(self):
        return self.width * self.height

    def perimeter(self):
        return 2 * (self.width + self.height)

    def contains(self, point):
        return (self.corner.x <= point.x < self.corner.x + self.width and
                self.corner.y <= point.y < self.corner.y + self.height)

class Circle:
    def __init__(self, center, radius):
        self.center = center
        self.radius = radius

    def area(self):
        return math.pi * self.radius ** 2

    def perimeter(self):
        return 2 * math.pi * self.radius

    def contains(self, point):
        return self.center.distance(point) < self.radius

将其保存为一个名为 `geometry.py` 的文件中，就可以作为一个模块使用了。在其他文件中，我们可以通过以下方式导入和使用：

from geometry import Point, Rectangle, Circle

p = Point(1, 2)
r = Rectangle(p, 10, 20)
c = Circle(p, 5)

print(r.area())  # 输出 200
print(c.perimeter())  # 输出 31.41592653589793
print(r.contains(Point(5, 5)))  # 输出 True