#裝飾器實現單例模式 def singleton1(func):instance={}def inner(*args,**kwargs):if func not in instance:instance[func]=func(*args,**kwargs)return instance[func]return inner @singleton1 class user():pass foo1=user() foo2=user() print(foo1 is foo2) #使用修改基類實現單例模式 class Singleton2():def __new__(cls, *args, **kwargs):if not hasattr(cls, '_instance'):cls._instance = super().__new__(cls, *args, **kwargs)return cls._instanceclass Foo(Singleton2):passfoo3 = Foo() foo4 = Foo()print( foo3 is foo4) #使用類實現單例模式，配合多線程 import threading import time class Singleton(object):_lock=threading.Lock()def __init__(self):time.sleep(1)@classmethoddef instance(cls, *args, **kwargs):if not hasattr(Singleton, "_instance"):with Singleton._lock:if not hasattr(Singleton, "_instance"):Singleton._instance = Singleton(*args, **kwargs)return Singleton._instancedef task(arg):obj = Singleton.instance()print(obj)for i in range(10):t = threading.Thread(target=task,args=[i,])t.start()time.sleep(20) obj=Singleton.instance() print(obj) #使用元類實現單例模式 class SingletonType(type):_instance_lock = threading.Lock()def __call__(cls, *args, **kwargs):if not hasattr(cls, "_instance"):with SingletonType._instance_lock:if not hasattr(cls, "_instance"):cls._instance = super(SingletonType,cls).__call__(*args, **kwargs)return cls._instanceclass Foo(metaclass=SingletonType):def __init__(self,name):self.name = nameobj1 = Foo('name') obj2 = Foo('name') print(obj1 is obj2)

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轉載于:https://www.cnblogs.com/lalalaxixixi/p/10467872.html

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