# class Singleton: # _instance = None # # def __init__(self): # print("init") # # @classmethod # def get_instance(cls): # if cls._instance is None: # cls._instance =cls() # return cls._instance # # # if __name__ == "__main__": # a = Singleton.get_instance() # b = Singleton.get_instance() # # print(a is b)
"""
运行结果
init
True
这是一个实现方法，获取当前实例，但是可以正常实例化它，因此它不会成为单例对象。 """ # 使用__new__ 创建实例，在创建类实例的时候会调用此方法，此方法在__init__之前已经调用过。 # # class Singleton: # _instance =None # # def __init__(self): # print("init") # # def __new__(cls, *args, **kwargs): # if cls._instance is None: # cls._instance = super().__new__(cls) # return cls._instance # # # if __name__ == '__main__': # a = Singleton() # b = Singleton() # print(a is b) # True
# 以上两种方式都不是线程安全 ，淫才十七称为线程安全，让我们LOCK y引入
import threading
import time
class ThreadingSingleton:
_instance =None
_lock=threading.Lock()
def __init__(self,name):
time.sleep(3)
self.name= name
# print("init")
def __new__(cls, *args, **kwargs):
with cls._lock:
if cls._instance is None:
cls._instance =super().__new__(cls)
return cls._instance
def __str__(self):
return str(self.name)
if __name__ == '__main__':
for i in range(10):
# print("i", i)
my = ThreadingSingleton(i)
print(my)
# 简单实用也安全实现线程模式，在初始化的时候 停止三秒 线程依然按照顺序执行，。
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