python - 为什么尝试通过 Python 属性设置 "points"会导致无限递归？

Question

为什么尝试通过 Python 属性设置“点”会导致无限递归？

使用 Python 3

import Task

myTask = Task.Task("Test",-5)

myTask.points = -7

print(myTask)

---

class Task:

def __init__(self,name="",points=0,times_done=0):
    self.name = name
    self.points = points
    self.times_done = times_done

@property
def points(self):
    return self.points

@points.setter
def points(self, points):
    if (points < 0):
        self.points = 0
    else:
        self.points = points

def __str__(self):
    return "The task '" + self.name + "' is worth " + str(self.points) + " and has been completed " + str(self.times_done) + " times."

---

当它尝试用值 -5 构造它时(应该通过属性将其设置为 0)，它会在设置函数/装饰 self.points = points 行上无限递归 @points.setter.

谢谢!

Answer 1

因为 self.points = ... 调用了 setter；在 setter 内部，self.points = ... 被执行，调用 setter；递归重复直到堆栈溢出。

通过使用其他名称，您可以防止递归:例如 self._points。

或者不使用 self.points = ...，而是使用 self.__dict__['points'] = ..(与 getter 相同):

@property
def points(self):
    return self.__dict__['points']

@points.setter
def points(self, points):
    if points < 0:
        self.__dict__['points'] = 0
    else:
        self.__dict__['points'] = points
    # self.__dict__['points'] = max(0, points)