python的WeakKeyDictionary类和weakref模块的其他函数
# -*- coding: utf-8 -*- # @Author : ydf # @Time : 2019/6/13 13:18 import time import weakref from app.utils_ydf import nb_print class A(): def __init__(self,x): self._x = x def __repr__(self): return f'A类的{self._x}实例 {id(self)}' def __del__(self): nb_print(f'摧毁啦 {self._x} 。。。。') wd = dict() # wd = weakref.WeakKeyDictionary() a1 = A(1) a2 = A(2) wd[a1] = 'xxxxxxx' wd[a2] = 'yyyyyyy' nb_print('销毁a1对象前') for item in wd.items(): nb_print(item) del a1 nb_print('销毁a1对象后') for item in wd.items(): nb_print(item) 
除此之外还有weakvaluedictionary和weakset这些对象。
weakref里面的函数。
class TestObj: def __init__(self): self.xx = 666 def test_func(reference): nb_print('Hello from Callback function!') nb_print(reference, 'This weak reference is no longer valid') t = TestObj() # 建立一个a的弱引用 nb_print(t.xx) t_ref = weakref.ref(t, test_func) nb_print(t_ref().xx) t.xx = 777 nb_print(t_ref().xx) del t nb_print(t_ref().xx) # 可以发现用不了了。