threading.local
多个线程修改同一个数据,复制多份变量给每个线程用,为每个线程开辟一块空间进行数据存储
# 不用local from threading import Thread import time lqz = -1 def task(arg): global lqz lqz = arg # time.sleep(2) print(lqz) for i in range(10): t = Thread(target=task,args=(i,)) t.start()
threading.local使用
from threading import Thread from threading import local import time from threading import get_ident # 特殊的对象 lqz = local() def task(arg): # 对象.val = 1/2/3/4/5 lqz.value = arg time.sleep(2) print(lqz.value) for i in range(10): t = Thread(target=task,args=(i,)) t.start()
from threading import get_ident,Thread import time storage = {} def set(k,v): ident = get_ident() 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()
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()
from threading import get_ident,Thread import time class Local(object): storage = {} def __setattr__(self, k, v): ident = get_ident() if ident in Local.storage: Local.storage[ident][k] = v else: Local.storage[ident] = {k: v} def __getattr__(self, k): ident = get_ident() return Local.storage[ident][k] obj = Local() def task(arg): obj.val = arg print(obj.val) for i in range(10): t = Thread(target=task,args=(i,)) t.start()
from threading import get_ident,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()
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()
#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))
请求上下文源码分析
请求上下文执行流程(ctx):
-0 flask项目一启动,有6个全局变量 -_request_ctx_stack:LocalStack对象 -_app_ctx_stack :LocalStack对象 -request : LocalProxy对象 -session : LocalProxy对象 -1 请求来了 app.__call__()---->内部执行:self.wsgi_app(environ, start_response) -2 wsgi_app() -2.1 执行:ctx = self.request_context(environ):返回一个RequestContext对象,并且封装了request(当次请求的request对象),session -2.2 执行: ctx.push():RequestContext对象的push方法 -2.2.1 push方法中中间位置有:_request_ctx_stack.push(self),self是ctx对象 -2.2.2 去_request_ctx_stack对象的类中找push方法(LocalStack中找push方法) -2.2.3 push方法源码: def push(self, obj): #通过反射找self._local,在init实例化的时候生成的:self._local = Local() #Local()flask封装的支持线程和协程的local对象 # 一开始取不到stack,返回None rv = getattr(self._local, "stack", None) if rv is None: #走到这,self._local.stack=[],rv=[] self._local.stack = rv = [] # 把ctx放到了列表中 #self._local={'线程id1':{'stack':[ctx,]},'线程id2':{'stack':[ctx,]},'线程id3':{'stack':[ctx,]}} rv.append(obj) return rv -3 如果在视图函数中使用request对象,比如:print(request) -3.1 会调用request对象的__str__方法,request类是:LocalProxy -3.2 LocalProxy中的__str__方法:lambda x: str(x._get_current_object()) -3.2.1 内部执行self._get_current_object() -3.2.2 _get_current_object()方法的源码如下: def _get_current_object(self): if not hasattr(self.__local, "__release_local__"): #self.__local() 在init的时候,实例化的,在init中:object.__setattr__(self, "_LocalProxy__local", local) # 用了隐藏属性 #self.__local 实例化该类的时候传入的local(偏函数的内存地址:partial(_lookup_req_object, "request")) #加括号返回,就会执行偏函数,也就是执行_lookup_req_object,不需要传参数了 #这个地方的返回值就是request对象(当此请求的request,没有乱) return self.__local() try: return getattr(self.__local, self.__name__) except AttributeError: raise RuntimeError("no object bound to %s" % self.__name__) -3.2.3 _lookup_req_object函数源码如下: def _lookup_req_object(name): #name是'request'字符串 #top方法是把第二步中放入的ctx取出来,因为都在一个线程内,当前取到的就是当次请求的ctx对象 top = _request_ctx_stack.top if top is None: raise RuntimeError(_request_ctx_err_msg) #通过反射,去ctx中把request对象返回 return getattr(top, name) -3.2.4 所以:print(request) 实质上是在打印当此请求的request对象的__str__ -4 如果在视图函数中使用request对象,比如:print(request.method):实质上是取到当次请求的reuquest对象的method属性 -5 最终,请求结束执行: ctx.auto_pop(error),把ctx移除掉
其他的东西:
-session: -请求来了opensession -ctx.push()---->也就是RequestContext类的push方法的最后的地方: if self.session is None: #self是ctx,ctx中有个app就是flask对象, self.app.session_interface也就是它:SecureCookieSessionInterface() session_interface = self.app.session_interface self.session = session_interface.open_session(self.app, self.request) if self.session is None: #经过上面还是None的话,生成了个空session self.session = session_interface.make_null_session(self.app) -请求走了savesession -response = self.full_dispatch_request() 方法内部:执行了before_first_request,before_request,视图函数,after_request,savesession -self.full_dispatch_request()---->执行:self.finalize_request(rv)-----》self.process_response(response)----》最后:self.session_interface.save_session(self, ctx.session, response) -请求扩展相关 before_first_request,before_request,after_request依次执行 -flask有一个请求上下文,一个应用上下文 -ctx: -是:RequestContext对象:封装了request和session -调用了:_request_ctx_stack.push(self)就是把:ctx放到了那个位置 -app_ctx: -是:AppContext(self) 对象:封装了当前的app和g -调用 _app_ctx_stack.push(self) 就是把:app_ctx放到了那个位置
g对象
专门用来存储用户信息的g对象,g的全称的为global
g对象在一次请求中的所有的代码的地方,都是可以使用的
session对象是可以跨request的,只要session还未失效,不同的request的请求会获取到同一个session,但是g对象不是,g对象不需要管过期时间,请求一次就g对象就改变了一次,或者重新赋值了一次