深入探讨Python中弱引用机制与应用

import weakref

# 创建对象
class MyClass:
    pass

obj = MyClass()

# 创建对象的弱引用
ref = weakref.ref(obj)

# 通过弱引用获取对象
print(ref())  # 输出: <__main__.MyClass object at 0x7f31e1f8d880>

# 删除对象的所有强引用
del obj

# 弱引用失效
print(ref())  # 输出: None

import weakref

# 创建弱引用字典
weak_dict = weakref.WeakValueDictionary()

# 创建对象
class MyClass:
    pass

obj1 = MyClass()
obj2 = MyClass()

# 将对象添加到弱引用字典
weak_dict['obj1'] = obj1
weak_dict['obj2'] = obj2

# 删除对象的所有强引用
del obj1, obj2

# 弱引用字典自动清理失效的弱引用
print(weak_dict)  # 输出: weakref.WeakValueDictionary({'obj2': <__main__.MyClass object at 0x7f31e1ebe730>})

import weakref

# 创建对象
class Node:
    def __init__(self, value):
        self.value = value
        self.next = None

# 创建循环引用
node1 = Node(1)
node2 = Node(2)
node1.next = node2
node2.next = node1

# 使用弱引用解决循环引用问题
weak_node1 = weakref.ref(node1)
weak_node2 = weakref.ref(node2)

# 删除对象的所有强引用
del node1, node2

# 弱引用失效
print(weak_node1())  # 输出: None
print(weak_node2())  # 输出: None

import weakref

# 创建对象缓存
class Cache:
    _cache = weakref.WeakValueDictionary()

    @classmethod
    def get_instance(cls, key):
        instance = cls._cache.get(key)
        if instance is None:
            instance = cls()
            cls._cache[key] = instance
        return instance