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自动跟踪属性值

python

Matina G · 技术社区 · 6 年前

假设我有一个类定义为:

class Wall(object):
    def __init__(self, color):
        self.color = color

我想自动跟踪颜色转换。也就是说,如果我将我的班级声明如下:

wall = Wall('red')

然后改变颜色:

wall.color = 'green'

我想自动得到一个名单

['green', 'red']

以这样的方式创建,如果我继续:

wall.color = ['yellow']

我得到清单:

['yellow', 'green']

等等。

到目前为止我所做的尝试都不起作用:

class Wall(object):

def __init__(self, color):
    self.color = color
    self._last_two_colors = [self.color, None]

def change_color(self, color):
    self._last_two_colors[1] = self._last_two_colors[0]
    self._last_two_colors[0] = self.color
    return self._last_two_colors

我的初始版本,不工作,很遗憾:

class Wall(object):

    def __init__(self, color):
        self._last_two_colors = []
        self.color = color

    @property
    def last_two_colors(self):
        return self._last_two_colors

    @last_two_colors.setter
    def last_two_colors(self):
        self._last_two_colors = [self.color]+self._last_two_colors
        self._last_two_colors = self._last_two_colors[:2]
        return self._last_two_colors

应该注意的是,我不希望调用方法change_color,它必须在更新颜色时自动调用。有什么主意吗? 事先谢谢。

2 回复 | 直到 6 年前

Michael H. 6 年前

In [14]: class Wall(object):
...: 
...:     def __init__(self, color):
...:         self.__last_two = [color, color]
...:         self.__color = color
...:     
...:     @property
...:     def color(self):
...:         return self.__color
...:     
...:     @color.setter
...:     def color(self, new_val):
...:         self.__color = new_val
...:         self.__last_two.pop(0)
...:         self.__last_two.append(new_val)
...:         print(self.__last_two)
...:  

In [15]: x = Wall(1)

In [16]: x.color
Out[16]: 1

In [17]: x.color = 2
[1, 2]

In [18]: x.color = 3
[2, 3]

In [19]: x.color = 4
[3, 4]

aldokkani 6 年前

property()

class Wall(object):

    def __init__(self, color):
        self._color = color
        self._color_transitions = [color]

    @property
    def color(self):
        """I'm the 'color' property."""
        return self._color

    @color.setter
    def color(self, value):
        if len(self._color_transitions) > 1:
            self._color_transitions.pop(0)
        self._color_transitions.append(value)
        self._color = value

    @property
    def color_transitions:
        return self._color_transitions