Python で特定のクラスのすべてのインスタンスを効果的に特定するにはどうすればよいですか?

<code class="python">import gc

for obj in gc.get_objects():
    if isinstance(obj, some_class):
        # Perform desired operations on 'obj'</code>

<code class="python">from collections import defaultdict
import weakref

class KeepRefs(object):
    # Dictionary to store weak references to class instances
    __refs__ = defaultdict(list)

    def __init__(self):
        # Add weak reference to self within class-level dictionary
        self.__refs__[self.__class__].append(weakref.ref(self))

    @classmethod
    def get_instances(cls):
        # Iterate through weak references and return valid instances
        for inst_ref in cls.__refs__[cls]:
            inst = inst_ref()
            if inst is not None:
                yield inst

class X(KeepRefs):
    def __init__(self, name):
        # Invoke base class constructor with required parameters
        super(X, self).__init__()
        self.name = name

# Create instances of class X
x = X("x")
y = X("y")

# Retrieve and print instance names
for r in X.get_instances():
    print(r.name)

# Remove one of the instances
del y

# Re-retrieve and print remaining instance names
for r in X.get_instances():
    print(r.name)</code>