python - 在 Python 中，当一个类使用另一个类时，反之亦然

Question

假设我有一个名为 Point 的类:

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

我还有一个名为 Line 的类，它在内部使用 Point:

class Line:
    #tail and head are supposed to be Point objects
    def __init__(self, tail, head):
        self.__tail = tail
        self.__head = head

问题是我希望 Point 有 reflect 方法，该方法只是相对于 Line line 反射点:

#Point class
def reflect(self, line):
    #Reflection code that uses Line methods

所以我在这里有交叉引用。问题是解决这个问题的最佳方法是什么？或者我应该避免这种方法？

Answer 1

不，没有交叉引用，没有循环，没有无限循环，也没有无限递归，一切都很清楚。你可以这样做:

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

    def reflect(self, line):  # line is a Line object
        reflected_x = None # replace w code to calc the reflection of x  vs. line
        reflected_y = None # replace w code to calc the reflection of y  vs. line
        return Point(reflected_x, reflected_y)

class Line:   # a Line defined by two Points 
    def __init__(self, tail, head):
        self.tail = tail
        self.head = head

我删除了变量中的双下划线，一开始就没有理由使用它。

或者:

(following Peter Wood advice in the comments): reflect should probably be a non-member function. It doesn't seem a natural property or behaviour of a Point. You don't want it to be a dumping ground for all your transformations. (hint - maybe create a Transformer object)

或者一个简单的函数，以一条线和一个点作为参数:

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


class Line:   # a Line defined by two Points 
    def __init__(self, tail, head):
        self.tail = tail
        self.head = head


def reflect(line, point):  # line is a Line object
    reflected_x = None # replace w code to calc the reflection of point.x  vs. line
    reflected_y = None # replace w code to calc the reflection of point.y  vs. line
    return Point(reflected_x, reflected_y)