local对象

一、local对象

1.1不使用local

# 不用local
from threading import Thread
import time
cxw = -1

def task(arg):
    global cxw
    cxw = arg
    time.sleep(2)
    print(cxw)

for i in range(10):
    t = Thread(target=task, args=(i,))
    t.start()

结果：9 9 9 9 9 9 9 9 9 9

1.2导入的local

from threading import Thread
from threading import local
import time

# 特殊的对象
cxw = local()
def task(arg):
    # 对象.val = 1/2/3/4/5
    cxw.value = arg

    time.sleep(2)

    print(cxw.value)
for i in range(10):
    t = Thread(target=task,args=(i,))
    t.start()

结果：0 2 3 4 6 5 8 7 9

1.3字典形式

from threading import get_ident, Thread
import time

storage = {}


def set(k, v):
    '''

    所有k都相同,根据线程的id不同来进行设置值
    :param k:
    :param v:
    :return:
    '''
    ident = get_ident()
    if ident in storage:
        storage[ident][k] = v
    else:
        storage[ident] = {k: v}


def get(k):
    """
    根据当前的线程id获取值
    :param k:
    :return:
    """
    ident = get_ident()
    return storage[ident][k]


def task(arg):
    set('val', arg)
    time.sleep(2)
    v = get('val')
    print(v)


for i in range(10):
    t = Thread(target=task, args=(i,))
    t.start()

结果：0 1 2 3 6 4 5 9 8 7

1.4面向对象的方式

from threading import get_ident, Thread
import time


class Local(object):
    storage = {}

    def set(self, k, v):
        ident = get_ident()
        if ident in Local.storage:
            Local.storage[ident][k] = v
        else:
            Local.storage[ident] = {k: v}

    def get(self, k):
        ident = get_ident()
        return Local.storage[ident][k]


obj = Local()


def task(arg):
    obj.set('val', arg)
    v = obj.get('val')
    print(v)


for i in range(10):
    t = Thread(target=task, args=(i,))
    t.start()

结果：0 1 2 3 6 4 5 9 8 7

1.5 每个对象都有自己的storage

# try...except...根据源码实现
try:
    from greenlet import getcurrent as get_ident
except Exception as e:
    from threading import get_ident
from threading import Thread
# from threading import get_ident,Thread
import time


class Local(object):
    def __init__(self):
        object.__setattr__(self, 'storage', {}) # 使用父类方式添加，否则__getattr__会出现递归
        # self.storage={}

    # storage={}

    def __setattr__(self, k, v):
        ident = get_ident()
        if ident in self.storage: # self.storage会到__getattr__中找，在__getattr__中没有没有也要找，自己调用自己，从而就导致了递归,疑惑：在__init__中已经产生创建了，怎们还会产生递归循环
            self.storage[ident][k] = v
        else:
            self.storage[ident] = {k: v}

    def __getattr__(self, k):
        ident = get_ident()
        return self.storage[ident][k]


obj = Local()
obj1 = Local()


def task(arg):
    obj.val = arg
    obj.xxx = arg
    print(obj.val)


for i in range(10):
    t = Thread(target=task, args=(i,))
    t.start()

结果：0 1 2 3 6 4 5 9 8 7