Python中如何序列化对象？序列化时如何避免循环引用？

import pickle

class MyClass:
    def __init__(self, data):
        self.data = data

obj = MyClass(123)

# 序列化到文件
with open('my_object.pkl', 'wb') as f:
    pickle.dump(obj, f)

# 从文件反序列化
with open('my_object.pkl', 'rb') as f:
    loaded_obj = pickle.load(f)

print(loaded_obj.data) # 输出: 123

import pickle

class Node:
    def __init__(self, name):
        self.name = name
        self.parent = None
        self.children = []

    def add_child(self, child):
        self.children.append(child)
        child.parent = self

node1 = Node("Node 1")
node2 = Node("Node 2")
node3 = Node("Node 3")

node1.add_child(node2)
node2.add_child(node3)
node3.add_child(node1)  # 循环引用

# 序列化前打破循环引用
node3.parent = None

# 序列化
serialized_data = pickle.dumps(node1)

# 反序列化
loaded_node1 = pickle.loads(serialized_data)

# 恢复循环引用（可选，如果需要的话）
# loaded_node3 = loaded_node1.children[0].children[0]
# loaded_node3.parent = loaded_node1

import pickle

class MyClass:
    def __init__(self, a, b, c):
        self.a = a
        self.b = b
        self.c = c

    def __getstate__(self):
        # 只序列化a和b
        return {'a': self.a, 'b': self.b}

    def __setstate__(self, state):
        # 恢复a和b，c设置为默认值
        self.a = state.get('a', 0)
        self.b = state.get('b', 0)
        self.c = -1  # 默认值

obj = MyClass(1, 2, 3)

# 序列化
serialized_data = pickle.dumps(obj)

# 反序列化
loaded_obj = pickle.loads(serialized_data)

print(loaded_obj.a, loaded_obj.b, loaded_obj.c) # 输出: 1 2 -1