threading.local作用及原理

先看下应用：

import threading

from threading import local

import time

obj = local()

def task(i):

    obj.xxxxx = i

    time.sleep()

    print(obj.xxxxx,i)

for i in range():

    t = threading.Thread(target=task,args=(i,))

    t.start()

上述代码实现了线程间的隔离，为每个线程开辟了独立的空间，这就是threading.local的作用

再看下面代码

import time

import threading

DIC = {}

def task(i):

    ident = threading.get_ident()

    if ident in DIC:

        DIC[ident]['xxxxx'] = i

    else:

        DIC[ident] = {'xxxxx':i }

    time.sleep()

    print(DIC[ident]['xxxxx'],i)

for i in range():

    t = threading.Thread(target=task,args=(i,))

    t.start()

上述代码使用字典实现了和threading.local一样的功能，其实就是threading.local实现的原理。

再看下面代码：

import time

import threading

import greenlet

DIC = {}

def task(i):

    # ident = threading.get_ident()

    ident = greenlet.getcurrent()

    if ident in DIC:

        DIC[ident]['xxxxx'] = i

    else:

        DIC[ident] = {'xxxxx':i }

    time.sleep()

    print(DIC[ident]['xxxxx'],i)

for i in range():

    t = threading.Thread(target=task,args=(i,))

    t.start()

上面代码就是threading.local功能的加强版：支持协程！

接着看：

import time

import threading

try:

    import greenlet

    get_ident =  greenlet.getcurrent

except Exception as e:

    get_ident = threading.get_ident

class Local(object):

    DIC = {}

    def __getattr__(self, item):

        ident = get_ident()

        if ident in self.DIC:

            return self.DIC[ident].get(item)

        return None

    def __setattr__(self, key, value):

        ident = get_ident()

        if ident in self.DIC:

            self.DIC[ident][key] = value

        else:

            self.DIC[ident] = {key:value}

obj = Local()

def task(i):

    obj.xxxxx = i

    time.sleep()

    print(obj.xxxxx,i)

for i in range():

    t = threading.Thread(target=task,args=(i,))

    t.start()

上述代码自己实现了threading.local的数据隔离，并支持协程。