如何在类构造函数中存储实例引用

class MyClass:
    def __init__(self):
        self.instance = self

    def some_method(self):
        print(self.instance)

my_obj = MyClass()
my_obj.some_method()  # 输出：<__main__.MyClass object at 0x7f9c9e7e6a90>

class MyClass:
    instance = None

    def __init__(self):
        MyClass.instance = self

    def some_method(self):
        print(MyClass.instance)

my_obj = MyClass()
my_obj.some_method()  # 输出：<__main__.MyClass object at 0x7f9c9e7e6a90>

instance = None

class MyClass:
    def __init__(self):
        global instance
        instance = self

    def some_method(self):
        print(instance)

my_obj = MyClass()
my_obj.some_method()  # 输出：<__main__.MyClass object at 0x7f9c9e7e6a90>