python单例的四种实现方式（线程安全）

from threading import Lock
from functools import wraps
def (func):
    func.__lock__ = Lock()
    def acquire_lock(*args, **kwargs):
        with func.__lock__:
            return func(*args, **kwargs)
    return acquire_lock
class Singleton1(object):
    """使用new方法"""
    @thread_safety
    def __new__(cls, *args, **kwargs):
        if not hasattr(cls, "_instance"):
            cls._instance = super(Singleton1, cls).__new__(cls, *args, **kwargs)
        return cls._instance
    def __repr__(self):
        return "类{}的实例对象id：{}".format(self.__class__.__name__, id(self))
class Singleton2(object):
    """使用相同属性"""
    _state = {}
    @thread_safety
    def __new__(cls, *args, **kwargs):
        instance = super(Singleton2, cls).__new__(cls, *args, **kwargs)
        instance.__dict__ = cls._state
        return instance
    def __repr__(self):
        return "类{}的实例对象id：{}".format(self.__class__.__name__, id(self))
def singleton(cls):
    instances = {}
    @wraps(cls)
    @thread_safety
    def _singleton(*args, **kwargs):
		"""使用装饰器"""
        if cls not in instances:
            instances[cls] = cls(*args, **kwargs)
        return instances[cls]
    return _singleton
@singleton
class Singleton3(object):
    def __init__(self, name):
        self.name = name
    def __repr__(self):
        return "类{}的实例对象id：{}".format(self.__class__.__name__, id(self))
if __name__ == '__main__':
    s1 = Singleton1()
    s2 = Singleton1()
    s3 = Singleton2()
    s3.name = "jordan"
    s4 = Singleton2()
    s5 = Singleton3(123)
    s6 = Singleton3(456)
    print(s1, s2, s1 is s2)
    print(s3, s4, s3 is s4, s3.name is s4.name)
    print(s5, s6, s5 is s6)