python中单例模式

# import ollama
# import chromadb
# from pathlib import Path
# import os
# import sys
# import io
# sys.stdout = io.TextIOWrapper(sys.stdout.buffer, encoding='utf-8')
# base_dir = Path(__file__).absolute().parent
# ollama_client = ollama.Client(host="http://localhost:11434")
# # client = chromadb.PersistentClient(path = os.path.join(base_dir,"ellis.db"))
# client = chromadb.HttpClient(
#    host="192.168.214.133",
#    port=31800
# )
# def analysis_doc(collectionname):
#   if collectionname in client.list_collections():
#     client.delete_collection(collectionname)
#   collection = client.create_collection(name=collectionname)
#   documents = [
#     "Ellis 今年33岁，性别男，是一个编程狂热爱好者,他也喜欢耍抖音，通常夜深人静了也在耍抖音",
#   ]

#   # store each document in a vector embedding database
#   for i, d in enumerate(documents):
#     response = ollama_client.embeddings(model="mxbai-embed-large", prompt=d)
#     embedding = response["embedding"]
#     if embedding:
#       collection.add(
#         ids=[str(i)],
#         embeddings=[embedding],
#         documents=[d]
#       )


# def ask_question(prompt="Ellis喜欢干什么",collectionname="docs"):
#   collection = client.get_collection(name=collectionname)

#   # generate an embedding for the prompt and retrieve the most relevant doc
#   response = ollama_client.embeddings(
#     prompt=prompt,
#     model="mxbai-embed-large"
#   )
#   results = collection.query(
#     query_embeddings=[response["embedding"]],
#     n_results=1
#   )
#   data = results['documents'][0][0]

#   # generate a response combining the prompt and data
#   output = ollama_client.generate(
#     model="llama3.2",
#     prompt=f"Using this data: {data}. Respond to this prompt: {prompt}"
#   )

#   print(output['response'])

  
# if __name__=='__main__':
#   analysis_doc("ellis")
#   ask_question(collectionname="ellis",prompt="ellis今年多大，爱好是什么")

import threading

class Singleton(type):
    _instances = {}
    _instance_lock = threading.Lock()

    def __call__(cls, *args, **kwargs):
        key = '&&'.join([str(i) for i in args])
        # 使用双重检查锁机制
        if key not in cls._instances:
            with cls._instance_lock:  # 确保线程安全
                if key not in cls._instances:  # 再次检查
                    cls._instances[key] = super(Singleton, cls).__call__(*args, **kwargs)
        return cls._instances[key]


class MyClass(metaclass=Singleton):
    def __init__(self, username):
        print(f"Initializing instance for {username}")
        self.username = username

    def get_username(self):
        return self.username


# 测试
a1 = MyClass("test")
print(a1.get_username())
a2 = MyClass("test")
print(a2.get_username())

    

debug可以发现，MyClass只实例化了一次

https://stackoverflow.com/questions/6760685/what-is-the-best-way-of-implementing-singleton-in-python