将类变为单例模式的装饰器

import threading
from functools import wraps


def singleton(cls):
    lock_ = threading.Lock()

    @wraps(cls)
    def wrapper(*args, **kwargs):
        if not hasattr(cls, "_instance"):
            with lock_:
                if not hasattr(cls, "_instance"):
                    cls._instance = cls(*args, **kwargs)
        return cls._instance

    return wrapper

# 使用说明
@singleton
class Lei(object):
	pass