python-flask-Source Flow

1. Start executing the App.run () in manage.py first

def run (self, host=none, Port=none, Debug=none, * *options)    :　　fromimport  Run_simple    　　try:        　　#Run_simple is a Werkzeug provided method that executes the third argument self ()        Run_simple (host, Port, self, **options)

Executes the app (), object () that represents the __call__ method of the calling object

    def __call__ (self, Environ, start_response):        return Self.wsgi_app (environ, start_response)

The App.wsgi_app method is also called

    defWsgi_app (self, Environ, start_response):#1.
CTX =Self.request_context (environ)
#Self.request_context #2. Ctx.push ()
Try:            Try:
#3.Response =self.full_dispatch_request ()exceptException as E:error=e Response=self.handle_exception (e)except: Error= Sys.exc_info () [1]                Raise            returnresponse (environ, start_response)finally:            ifSelf.should_ignore_error (Error): Error=None Ctx.auto_pop (Error)

1th Step: Execute the App. Request_context Method, the information of the request is passed in.

    def Request_context (self, environ):         return RequestContext (self, environ)

Returns an instance object of the RequestContext class

    def __init__ (self, app, environ, request=None):         = App        if is None:            =
　　　　　　  #App.request_class = Request               = request        = None

Notice in the init construction method that the app also calls the Request_class method, which is the request instance an object,

So far we know:

CTX is a RequestContext object, which encapsulates two main properties, one is the object of self.request = Request instance, and the request object encapsulates all the data requested in.
The other one is self.session = None  .

2nd step: Execute the ctx.push () method

Because CTX is the object of the RequestContext class, we're going to find the push method in the RequestContext class.

    defpush (self): #1. App_ctx=_app_ctx_stack.topifApp_ctx isNoneorApp_ctx.app! =Self.app:app_ctx=Self.app.app_context ()
# Self.app.app_context = app.app_context = AppContext (APP) App_ctx.push ()
#2.
_request_ctx_stack.push (self)
#_request_ctx_stack = Localstack ()
#3.
Self.session = Self.app.open_session (self.request)

When #判断没有 Secret_key:
If Self.session is None:
Self.session = Self.app.make_null_session ()
#raise RuntimeError (' The session is unavailable because no secret ' key was set.)

1th step: To the _app_ctx_stack this stack to take the last data, if not fetch or fetch the app is not the current app, call the app. the App_context () method is a new instance of an App object that executes the app. push () method (in this again, because the app is a AppContext object, first go to the AppContext class to find the Push method),

    def push (self):         _app_ctx_stack.push (self)     #把新创建的app对象添加到了_app_ctx_stack in this stack        appcontext_ Pushed.send (Self.app)   #在这里遇到了第一个信号, executes when requesting app context push 

2nd step:Call the Push method for an object of the Localstack class

    def push (self, obj): ' Stack' , None) #self. _local = local ()                 
　　　　      #第一次的时候rv肯定是None         if  is None:             = RV = []      #Local对象.  stack = RV = []  executes the __setattr__ method of the object        rv.append (obj)        return RV

Try:     fromGreenletImportGetCurrent as Get_identexceptImporterror:Try:         fromThreadImportget_identexceptImporterror: from_threadImportget_identclassLocal (object):
def __init__ (self):
Object.__setattr__ (self, ' __storage__ ', {}) #这里为什么用object.__setattr__ instead of using self directly. __storage__={}
Object.__setattr__ (self, ' __ident_func__ ', get_ident) #如果用self的方式设置属性, will trigger the self's __setattr__ method, will be infinite loop
　　    def __setattr__(self, Name, value): Ident= self.__ident_func__() Storage= self.__storage__        Try: Storage[ident][name]=valueexceptKeyerror:storage[ident]= {Name:value}

python-flask-Source Flow