Flask之上下文管理和flash_session的使用

上下文管进阶理解

 1.偏函数

import functools
def index(a1,a2):
    return a1 + a2
# 原来的调用方式
# ret = index(1,23)
# print(ret)
# 偏函数，帮助开发者自动传递参数
new_func = functools.partial(index,666)
ret = new_func(1)
print(ret)

 2.执行父类方法

class Base(object):
    def func(self):
        print('Base.func')
class Foo(Base):
    def func(self):
        # 方式一：根据mro的顺序执行方法
        # super(Foo,self).func()
        # 方式二：主动执行Base类的方法
        # Base.func(self)

        print('Foo.func')
obj = Foo()
obj.func()

# print(Foo.__mro__)

 3、面向对象的特殊方法

一
class Foo(object):
    def __init__(self):
        self.storage = {}
        # object.__setattr__(self,'storage',{})

    def __setattr__(self, key, value):
        print(key,value)

obj = Foo()
obj.xx = 123

结果
storage {}
xx 123

二
class Foo(object):
    def __init__(self):
        self.storage = {}
        # object.__setattr__(self,'storage',{})

    def __setattr__(self, key, value):
        print(key,value,self.storage)  # 打印self.storage会报错，因为实例化对象先执行
        #init，init中self.storage会触发seattr方法，seattr中的self.storge没有定义

obj = Foo()
obj.xx = 123


三
class Foo(object):
    def __init__(self):
        # self.storage = {}
        object.__setattr__(self,'storage',{})

    def __setattr__(self, key, value):
        print(key,value,self.storage)

obj = Foo()
obj.xx = 123

 4、Flask  Local源码

local是用来给每个线程或者协程开辟一个空间

 

try:
    from greenlet import getcurrent as get_ident
except:
    from threading import get_ident
class Local(object):
    __slots__ = ('__storage__', '__ident_func__')

    def __init__(self):
        # __storage__ = {1231:{'stack':[]}}
        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)

 

 5、LocalStack源码

localstack 维护local的列表,维护成一个栈

 

class LocalStack(object):
    def __init__(self):
        self._local = Local()

    def push(self,value):
        rv = getattr(self._local, 'stack', None) # self._local.stack =>local.getattr
        if rv is None:
            self._local.stack = rv = [] #  self._local.stack =>local.setattr
        rv.append(value) # self._local.stack.append(666)
        return rv


    def pop(self):
        """Removes the topmost item from the stack, will return the
        old value or `None` if the stack was already empty.
        """
        stack = getattr(self._local, 'stack', None)
        if stack is None:
            return None
        elif len(stack) == 1:
            return stack[-1]
        else:
            return stack.pop()

    def top(self):
        try:
            return self._local.stack[-1]
        except (AttributeError, IndexError):
            return None

 

 源码入口

app.__call__
app.wsgi_app

 上下文管理request简易流程图

 flash_session的使用

flask-session 
    
        pip3 install flask-session 
        
        掌握：
            - 使用
            
                import redis
                from flask import Flask,request,session
                from flask.sessions import SecureCookieSessionInterface
                from flask_session import Session

                app = Flask(__name__)

                # app.session_interface = SecureCookieSessionInterface()
                # app.session_interface = RedisSessionInterface()
                app.config['SESSION_TYPE'] = 'redis'
                app.config['SESSION_REDIS'] = redis.Redis(host='140.143.227.206',port=6379,password='1234')
                Session(app)

                @app.route('/login')
                def login():
                    session['user'] = 'alex'
                    return 'asdfasfd'

                @app.route('/home')
                def index():
                    print(session.get('user'))

                    return '...'


                if __name__ == '__main__':
                    app.run()
            - 原理：
                - session数据保存到redis
                    session:随机字符串1:q23asifaksdfkajsdfasdf
                    session:随机字符串2:q23asifaksdfkajsdfasdf
                    session:随机字符串3:q23asifaksdfkajsdfasdf
                    session:随机字符串4:q23asifaksdfkajsdfasdf
                    session:随机字符串5:q23asifaksdfkajsdfasdf
                - 随机字符串返回给用户。
                    随机字符串
                
                
                源码：
                    from flask_session import RedisSessionInterface