Flask的基础二

一、session

除请求对象之外，还有一个 session 对象。它允许你在不同请求间存储特定用户的信息。它是在 Cookies 的基础上实现的，并且对 Cookies 进行密钥签名要使用会话，你需要设置一个密钥。

设置：session['username'] ＝ 'xxx'
取值：session.get['username']
删除：session.pop('username', None)

from flask import Flask

from flask import render_template

from flask import session

from flask import request

from flask import redirect

app = Flask(__name__)

app.config.from_mapping({"SECRET_KEY":"value"})

@app.route("/login",methods=["GET","POST"])

def login():

    if request.method == "POST":

        username = request.form.get("username")

        password = request.form.get("password")

        if username == "xiaoming" and password == "":

            # 登陆成功后设置session

            session["userinfo"] = {"name":username}

            return redirect("/")

    return render_template("login.html")

@app.route("/")

def index():

    # 获取session

    print(session["userinfo"])

    return "首页"

if __name__ == '__main__':

    app.run()

二、flash 闪现

闪现的作用：flash设置值只能取一次

闪现的原理：利用session设置值，通过pop的方法删除并返回值，取值的时候调用session.pop()的方法将值放到flashes中，请求还在取值都从flashes中获取

'''

存一次只能取一次值，用session模拟闪现

'''

from flask import Flask,session

app = Flask(__name__)

app.secret_key = "key"      # 设置session需要设置secret_key

@app.route("/set")

def set():

    session['name'] = "xiaoming"

    return "Set name"

@app.route("/get")

def get():

    # 删除session的键值对并取值

    name = session.pop("name","")

    print(name)

    return name

if __name__ == '__main__':

    app.run()

session模拟flash

# 设置值

flash(message, category='message')

# 获取值

get_flashed_messages(with_categories=False, category_filter=[])

from flask import Flask,flash,get_flashed_messages

app = Flask(__name__)

app.secret_key = "key"

@app.route("/set")

def set():

    flash("xiaoming")   # 设置值

    flash(18,"age")     # 参数：message,分类

    return "flash设置值"

@app.route("/get")

def get():

    # 取值

    name = get_flashed_messages()  

    # 按分类取值category_filter=[]

    age = get_flashed_messages(category_filter=["age"])

    print(name)

    print(age)

    return "GET"

if __name__ == '__main__':

    app.run()

三、中间件

app.run()        #程序的入口

run_simple(host, port, self, **options)        # run的本质是调用run_simple

# host == ip

# port == 端口

# self == app

# 执行了self() 相当于执行app(),调用app的__call__方法

# app.__call__

def __call__(self, environ, start_response):

    return self.wsgi_app(environ, start_response)

# 相当于执行 app.wsgi_app(environ, start_response)

app.run的源码流程

'''

中间件的实现

'''

from flask import Flask

app = Flask(__name__)

class Middleware(object):

    def __init__(self,old_wsgi_app):

        # 原来的wsgi_app

        self.wsgi_app= old_wsgi_app

    def __call__(self, *args, **kwargs):

        print("项目启动之前")

        # wsgi_app是原来的wsgi_app

        ret = self.wsgi_app(*args, **kwargs)

        print("项目启动之后")

        return ret

if __name__ == '__main__':

    # 将旧的app.wsgi_app赋值给新的app.wsgi_app

    app.wsgi_app = Middleware(app.wsgi_app)

    app.run()

'''

 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)

项目启动之前

127.0.0.1 - - [28/Dec/2018 16:43:27] "GET / HTTP/1.1" 404 -

项目启动之后

'''

四、特殊的装饰器

@app.before_first_request # 第一次请求
@app.before_request # 每一次请求
@app.after_request # 每一次响应

注意：before_request有返回值，不走视图函数，直接走after_request
@app.template_global()
@app.template_filter()
@app.errorhandler(404)

'''

自定义装饰器实现登陆认证

'''

from flask import Flask

from functools import wraps

from flask import url_for

from flask import session

from flask import render_template

from flask import request,redirect

app = Flask(__name__)

app.secret_key = "key"

# 自定义装饰器

def Auth_decorator(func):

    @wraps(func)

    def inner(*args,**kwargs):

        # 访问是否携带认证，否则跳转都登陆页面

        if not session.get("user",""):

            return redirect("login")

        ret = func(*args,**kwargs)

        return ret

    return inner

# 登陆

@app.route("/login",endpoint="login",methods=["GET","POST"])

def login():

    if request.method == "POST":

        username = request.form.get("username")

        password = request.form.get("password")

        if username == "xiaoming" and password == "":

            # 登陆成功后设置session

            session["user"] = username

            return redirect(url_for("myhome"))

    return render_template("login.html")

# 登陆成功后跳转的页面

@app.route("/home",endpoint="myhome")

@Auth_decorator

def home():

    return "登陆成功的HOME页面"

if __name__ == '__main__':

    app.run()

自定义登陆认证的装饰器

# 模板的全局装饰器

@app.template_global()

def mysum(n1,n2):

    return n1+n2

# HTML

{{ mysum(10,5) }}

@app.template_global()

# 模板的筛选器

@app.template_filter()

def myfilter(data):

    return data[::2]

# HTML

{{ "today hello" | myfilter() }}

模板的筛选器

# 路径不存在跳转到指定页面的装饰器

@app.errorhandler(404)

def error_page(error):

    return render_template("error404.html")

路径不存在返回页面

五、路由的实现原理

不能有多个endpoint指向同一个视图函数，内部是{'endpoint':"view_func"}

app.route()

# 执行route函数

route(self, rule, **options)

# self == app

# rule == 路由

# 返回decorator函数

return decorator

# decorator函数，传入视图函数

def decorator(f):

    endpoint = options.pop('endpoint', None)

    self.add_url_rule(rule, endpoint, f, **options)

    return f

# 调用add_url_rule(路由,endpoint,视图函数)

def add_url_rule(self, rule, endpoint=None, view_func=None,provide_automatic_options=None, **options):

    # endpoint不能有多个视图函数，否则抛出异常

    if view_func is not None:

        old_func = self.view_functions.get(endpoint)

        if old_func is not None and old_func != view_func:

            raise AssertionError('View function mapping is overwriting an '

                                 'existing endpoint function: %s' % endpoint)

        self.view_functions[endpoint] = view_func

route源码流程

'''

根据路由原理创建Flask项目

'''

from flask import Flask

# 实例化Flask对象

app = Flask(__name__)

def index():

    return "这是首页"

# 调用app.route的核心方法，实行app.route

app.add_url_rule("/",view_func=index)

if __name__ == '__main__':

    app.run()

六、CBV编程

1.类继承views.MethodView
2.装饰器修饰的列表 decorators = []
3.指定路由和类 app.add_url_rule

from flask import Flask

from flask import views

app = Flask(__name__)

class MyView(views.MethodView):

    # decorators = []               # 存放装饰器的列表

    # methods = ["GET","POST"]      # 请求方式列表，用于限制的

    def get(self):

        return "GET"

    def post(self):

        return "POST"

app.add_url_rule("/",view_func=MyView.as_view(name="index"))

if __name__ == '__main__':

    app.run()

七、自定义路由正则匹配

from flask import Flask,url_for

from werkzeug.routing import BaseConverter

app = Flask(__name__)

class RegexConverter(BaseConverter):

    '''

    自定义URL匹配正则表达式

    '''

    def __init__(self,map,regex):

        super(RegexConverter,self).__init__(map)

        self.regex = regex

    def to_python(self, value):

        '''

        路由匹配时，匹配成功后传递给视图函数中参数的值

        :param value:

        :return:

        '''

        return value

    def to_url(self, value):

        '''

        使用url_for反向生成URL时，传递的参数经过该方法处理，返回的值用于生成URL中的参数

        :param value:

        :return:

        '''

        val = super(RegexConverter,self).to_url(value)

        return val

# 添加到flask中

app.url_map.converters['regex'] = RegexConverter

@app.route("/index/<regex('\d+'):id>")

def index(id):

    print(url_for('index',id=''))

    print(type(id))

    return "{}".format(id)

if __name__ == '__main__':

    app.run()

巴特西

Flask的基础二

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