如何可靠触发Python对象的__del__方法？

我希望对象被销毁时能立即、可靠地调用其__del__方法。我知道Python 2里存在相关问题，但Python 3文档明确说明当引用计数为0时会调用__del__，可我的程序并未达到预期效果：

import time

class MyClass:
    object_list = []
    def __init__(self):
        MyClass.object_list.append(self)
        print("object initialized")
    def __del__(self):
        print("executing cleanup steps")
        MyClass.object_list.remove(self)

a = MyClass()
b = MyClass()
c = MyClass()
print(len(MyClass.object_list))
del b
time.sleep(1)
print("sleep finished")
print(len(MyClass.object_list))

我想要实现的目标是：对象销毁时立即将b从object_list中移除，同时让变量b无法访问。仅调用b.__del__()并不足够，还需让b不可访问。需要注意的是：先调用b.__del__()再执行del b会导致Python解释器退出时报错。

有意思的是，一个结构非常相似的程序在执行del b时会立即调用b.__del__()：

import time

class MyClass:
    counter = 0
    def __init__(self, value):
        self.value = value
        print("object initialized")
        MyClass.counter+=1
    def __del__(self):
        print("executing cleanup steps")
        MyClass.counter-=1

a = MyClass(5)
b = MyClass(6)
c = MyClass(7)
print(MyClass.counter)
del b
time.sleep(1)
print("sleep finished")
print(MyClass.counter)

编辑
@Pranav Hosangadi指出object_list中仍保留着对象的引用，这是我的疏忽。现在我想到一个临时解决方案：先调用b.__del__()再执行del b，但这是两步操作，我希望能一步完成：

import time

class MyClass:
    object_list = []
    def __init__(self, value):
        self.value = value
        MyClass.object_list.append(self)
        print("object initialized")
    def __del__(self):
        print("executing cleanup steps")
        try:
            MyClass.object_list.remove(self)
        except:
            pass

a = MyClass(1)
b = MyClass(2)
c = MyClass(3)
print(len(MyClass.object_list))
b.__del__()
del b
time.sleep(1)
print("sleep finished")
print(len(MyClass.object_list))

内容的提问来源于stack exchange，提问作者laolux