Flask快速入门(12) — local与偏函数
目录
多个线程修改同一个数据，复制多份变量给每个线程用，比如我们用的request，怎样让不同的请求有自己的request。就是为每个线程开辟一块空间进行数据存储
不用threading.local
from threading import Thread
import time
ctx = -1
def task(arg):
global ctx
ctx = arg
# time.sleep(2)
print(ctx)
for i in range(10):
t = Thread(target=task,args=(i,))
t.start()
使用threading.local
from threading import Thread,local
# 特殊的对象
ctx = local()
def task(arg):
ctx.value = arg
# time.sleep(2)
print(ctx.value)
for i in range(10):
t = Thread(target=task,args=(i,))
t.start()
通过字典自定义threading.local（函数）
from threading import Thread, get_ident
storage = {}
def set(k, v):
ident = get_ident() # 获取线程id
if ident in storage:
storage[ident][k] = v
else:
storage[ident] = {k: v}
def get(k):
ident = get_ident()
return storage[ident][k]
def task(arg):
set('val', arg)
v = get('val')
print(v)
for i in range(10):
t = Thread(target=task, args=(i,))
t.start()
面向对象版
from threading import Thread,get_ident
class Local(object):
storage = {}
def get(self,k):
ident = get_ident()
return Local.storage[ident][k]
def set(self,k,v):
ident = get_ident()
if ident in Local.storage:
Local.storage[ident][k] = v
else:
Local.storage[ident] = {k:v}
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()
通过setattr和getattr实现
from threading import Thread,get_ident
class Local(object):
storage = {}
def __setattr__(self, key, value):
ident = get_ident()
if ident in self.storage:
self.storage[ident][key] = value
else:
self.storage[ident] = {key:value}
def __getattr__(self, key):
ident = get_ident()
return self.storage[ident][key]
obj = Local()
def task(arg):
obj.value = arg
print(obj.value)
for i in range(10):
t = Thread(target=task,args=(i,))
t.start()
每个对象有自己的存储空间（字典）
from threading import Thread,get_ident
class Local(object):
def __init__(self):
object.__setattr__(self,'storage',{})
# self.storage = {}
def __setattr__(self, key, value):
ident = get_ident()
if ident in self.storage:
self.storage[ident][key] = value
else:
self.storage[ident] = {key:value}
def __getattr__(self, key):
ident = get_ident()
return self.storage[ident][key]
obj = Local()
def task(arg):
obj.value = arg
print(obj.value)
for i in range(10):
t = Thread(target=task,args=(i,))
t.start()
兼容线程和协程（源码到request中去看，看local的__getattr__,setattr）
# 如果是协程get_ident获取的是协程id
try:
from greenlet import getcurrent as get_ident
except Exception as e:
from threading import get_ident
from threading import Thread
import time
class Local(object):
def __init__(self):
object.__setattr__(self,'storage',{})
def __setattr__(self, k, v):
ident = get_ident()
if ident in self.storage:
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()
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()
partial偏函数
# 偏函数的第二个部分(可变参数)，按原有函数的参数顺序进行补充，参数将作用在原函数上，最后偏函数返回一个新函数
from functools import partial
def test(a,b,c,d):
return a+b+c+d
tes=partial(test,1,2)
print(tes(3,4))
