小黑腰酸背痛腿抽筋的日常积累：多线程单例模式

错误结果的单例模式

import threading
import time

class Singleton:
    instance = None

    def __init__(self, name):
        self.name = name

    def __new__(cls, *args, **kwargs):
        if cls.instance:
            return cls.instance

        time.sleep(0.1)
        cls.instance = object.__new__(cls)
        return cls.instance

def task():
    obj = Singleton('x')
    print(obj)

if __name__ == '__main__':
    for i in range(10):
        t = threading.Thread(target=task)
        t.start()
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<main.Singleton object at 0x0000021929B00AC0>
<main.Singleton object at 0x0000021929A67C40><main.Singleton object at 0x0000021929B0A9A0>
<main.Singleton object at 0x0000021929A66CA0>
<main.Singleton object at 0x0000021929AF0880><main.Singleton object at 0x0000021929B0A9A0>

<main.Singleton object at 0x0000021929A67C40>
<main.Singleton object at 0x000002192C8991F0>
<main.Singleton object at 0x000002192C8BFA60><main.Singleton object at 0x0000021929A3DC10>

Process finished with exit code 0

加锁的单例模式

import threading
import time

class Singleton:
    instance = None
    lock = threading.RLock()

    def __init__(self,name):
        self.name = name

    def __new__(cls,*args,**kwargs):
        with cls.lock:
            if cls.instance:
                return cls.instance
            time.sleep(0.1)
            cls.instance = object.__new__(cls)
        return cls.instance
def task():
    obj = Singleton('x')
    print(obj)

if __name__ == '__main__':
    for i in range(10):
        t = threading.Thread(target=task)
        t.start()

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<main.Singleton object at 0x000002AD30B81AC0><main.Singleton object at 0x000002AD30B81AC0>

<main.Singleton object at 0x000002AD30B81AC0><main.Singleton object at 0x000002AD30B81AC0>
<main.Singleton object at 0x000002AD30B81AC0>
<main.Singleton object at 0x000002AD30B81AC0>

<main.Singleton object at 0x000002AD30B81AC0><main.Singleton object at 0x000002AD30B81AC0><main.Singleton object at 0x000002AD30B81AC0><main.Singleton object at 0x000002AD30B81AC0>

加判断进一步提升性能

import threading
import time

class Singleton:
    instance = None
    lock = threading.RLock()

    def __init__(self,name):
        self.name = name

    def __new__(cls,*args,**kwargs):
        if cls.instance:
            return cls.instance
        with cls.lock:
            if cls.instance:
                return cls.instance
            time.sleep(0.1)
            cls.instance = object.__new__(cls)
        return cls.instance
def task():
    obj = Singleton('x')
    print(obj)

if __name__ == '__main__':
    for i in range(10):
        t = threading.Thread(target=task)
        t.start()
    data = Singleton('ssssssssss')
    print(data)
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<main.Singleton object at 0x00000157B600B4F0><main.Singleton object at 0x00000157B600B4F0>

<main.Singleton object at 0x00000157B600B4F0>
<main.Singleton object at 0x00000157B600B4F0><main.Singleton object at 0x00000157B600B4F0>

<main.Singleton object at 0x00000157B600B4F0>
<main.Singleton object at 0x00000157B600B4F0><main.Singleton object at 0x00000157B600B4F0>

<main.Singleton object at 0x00000157B600B4F0><main.Singleton object at 0x00000157B600B4F0>

<main.Singleton object at 0x00000157B600B4F0>

Process finished with exit code 0

小黑生活

去领取马拉松物资

晚上去按个摩啦，按了一个半小时

出发跑北京马拉松啦

看到了爱跑步的李老师和明哥

一起跑就跟着330的官兔

跑到30km了，膝盖突然剧痛，但还是边跑边走挺过了最后的10km

请添加图片描述

马拉松掠影，感谢坚强的小黑

![请添加图片描述](https://img-blog.csdnimg.cn/a7aa603aa7ad4bb5a36207cf65750110.jpeg

一瘸一拐坐上了回学校的公交，跟中老黑小吃一顿

来自网上的恐惧

通过这次马拉松，小黑会越来越坚强，约在意终点越抵达不了，享受旅途，成长自己~