Flask之线程与协程
2021-04-22 12:30
标签：click hide key sed getc getattr where text error: 还记得在flask中是怎么引入request对象的吗？没错是通过： 那么，这样全局引入的，势必会存在下面的问题，如果多个用户同时发送请求，一个request对象会被多个用户修改，最后大家拿到的返回值就都是最后一个用户的返回值，那么应该如何解决这种问题呢？ 通过上面的例子可以看出threading.local()对象的作用就是为每一个线程开辟一个独有的空间，用于保存每一个线程自己独有的值，这样不至于一个值被多个线程改来改去造成数据的混乱。 对于flask中的request有下面三种情况： 那么，如果在flask中支持协程，应该怎么实现呢？ 如果要支持线程，可以自定义类似threading.local()对象，那么它是在threading.local()对象的基础上进一步强化，可以支持协程。 在flask的源码werkzeug.local.py文件中： 参考源码可以自己写的Local对象进行优化： Flask之线程与协程 标签：click hide key sed getc getattr where text error: 原文地址：https://www.cnblogs.com/shenjianping/p/13269731.html一、前言
from flask import request
（一）threadinglocal
import threading
local_values = threading.local()
def func(num):
local_values.num_ = num
print(local_values.num_, threading.current_thread().name)
for i in range(10):
t = threading.Thread(target=func, args=(i,), name=‘线程%s‘ % i)
t.start()
"""
输出：
0 线程0
1 线程1
2 线程2
3 线程3
4 线程4
5 线程5
6 线程6
7 线程7
8 线程8
9 线程9
"""
（二）request对象
二、自定义支持协程和协程的Local对象
import threading
from threading import get_ident
class Local:
def __init__(self):
self.storage = {} #会生成字典 {5936: {‘num_‘: 3}, 7796: {‘num_‘: 6}, 7056: {‘num_‘: 7}...}
self.get_ident = get_ident
def set(self,k,v):
ident = self.get_ident()
origin = self.storage.get(ident)
if not origin:
origin = {k:v}
else:
origin[k] = v
self.storage[ident] = origin
def get(self,k):
ident = self.get_ident()
origin = self.storage.get(ident)
if not origin:
return None
return origin.get(k,None)
local_values = Local()
def task(num):
local_values.set(‘num_‘,num)
print(local_values.get(‘num_‘),threading.current_thread().name)
if __name__ == ‘__main__‘:
for i in range(10):
t = threading.Thread(target=task,args=(i,),name=‘线程%s‘%i)
t.start()
"""
输出
0 线程0
1 线程1
2 线程2
3 线程3
4 线程4
5 线程5
6 线程6
7 线程7
8 线程8
9 线程9
"""
# since each thread has its own greenlet we can just use those as identifiers
# for the context. If greenlets are not available we fall back to the
# current thread ident depending on where it is.
try:
from greenlet import getcurrent as get_ident
except ImportError:
try:
from thread import get_ident
except ImportError:
from _thread import get_ident
class Local(object):
__slots__ = ("__storage__", "__ident_func__")
def __init__(self):
object.__setattr__(self, "__storage__", {})
object.__setattr__(self, "__ident_func__", get_ident)
def __iter__(self):
return iter(self.__storage__.items())
def __call__(self, proxy):
"""Create a proxy for a name."""
return LocalProxy(self, proxy)
def __release_local__(self):
self.__storage__.pop(self.__ident_func__(), None)
def __getattr__(self, name):
try:
return self.__storage__[self.__ident_func__()][name]
except KeyError:
raise AttributeError(name)
def __setattr__(self, name, value):
ident = self.__ident_func__()
storage = self.__storage__
try:
storage[ident][name] = value
except KeyError:
storage[ident] = {name: value}
def __delattr__(self, name):
try:
del self.__storage__[self.__ident_func__()][name]
except KeyError:
raise AttributeError(name)
import threading
try:
from greenlet import getcurrent as get_ident # 协程
except ImportError:
try:
from thread import get_ident
except ImportError:
from _thread import get_ident # 线程
class Local(object):
def __init__(self):
object.__setattr__(self, ‘__storage__‘, {})
object.__setattr__(self, ‘__ident_func__‘, get_ident)
def __getattr__(self, name):
try:
return self.__storage__[self.__ident_func__()][name]
except KeyError:
raise AttributeError(name)
def __setattr__(self, name, value):
ident = self.__ident_func__()
storage = self.__storage__
try:
storage[ident][name] = value
except KeyError:
storage[ident] = {name: value}
def __delattr__(self, name):
try:
del self.__storage__[self.__ident_func__()][name]
except KeyError:
raise AttributeError(name)
local_values = Local()
def task(num):
local_values.num_ = num # 通过对象.key=value的方式触发__setattr__方法
print(local_values.num_, threading.current_thread().name) # 通过对象.key触发__getattr__方法
if __name__ == ‘__main__‘:
for i in range(10):
t = threading.Thread(target=task, args=(i,), name=‘线程%s‘ % i)
t.start()
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