[flask]基础知识

Flask 基础知识

基本框架结构

from flask import Flask
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
from database_setup import Base, Restaurant, MenuItem

app = Flask(__name__)

engine = create_engine('sqlite:///restaurantmenu.db')
Base.metadata.bind = engine

DBSession = sessionmaker(bind=engine)
session = DBSession()


@app.route('/')
@app.route('/hello')
def HelloWorld():
    restaurant = session.query(Restaurant).first()
    items = session.query(MenuItem).filter_by(restaurant_id=restaurant.id)
    output = ''
    for i in items:
        output += i.name
        output += '
'
        output += i.price
        output += '
'
        output += i.description
        output += '
'
        output += '
'
    return output

if __name__ == '__main__':
    app.debug = True
    app.run(host='0.0.0.0', port=5000)

路由 route

Flask Documentation on Routing :
http://flask.pocoo.org/docs/0.10/quickstart/#routing
flask路由的格式为/path//path
其中，type可以为string, int, path

模板 template

HTML Character Escaping is a way of writing special characters inside of HTML code, this is a different concept from the HTML escaping with python code
注意模板文件都应该放入名为templates的文件夹。

URL-Buiding : url_for

url_for 用来将模板里的超链接转化为flask定义的后端接口函数。例如：
./templates/menu.html

<h1>{{restaurant.name}}h1>

{% for i in items %}
<br>
<h2>{{i.name}}h2>
{{i.description}}
<br>
{{i.price}}
Edita>
Deletea>
<br>
<br>
{% endfor %}

./flask_server.py

import flask
from flask import Flask
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
from database_setup import Base, Restaurant, MenuItem

app = Flask(__name__)

engine = create_engine('sqlite:///restaurantmenu.db')
Base.metadata.bind = engine

DBSession = sessionmaker(bind=engine)
session = DBSession()


@app.route('/')
@app.route('/hello')
def HelloWorld():
    restaurant = session.query(Restaurant).first()
    items = session.query(MenuItem).filter_by(restaurant_id=restaurant.id)
    output = ''
    for i in items:
        output += i.name
        output += '
'
        output += i.price
        output += '
'
        output += i.description
        output += '
'
        output += '
'
    return output

@app.route("/restaurant//new")
def new_menu_item(restaurant_id):
    return "create new menu item for the Restaurant(id={})".format(restaurant_id)

@app.route("/restaurant//edit/")
def edit_menu_item(restaurant_id, menu_id):
    return "edit the Menu(id={}) in Restaurant(id={})".format(menu_id, restaurant_id)

@app.route("/restaurant//delete/")
def delete_menu_item(restaurant_id, menu_id):
    return "delete the Menu(id={}) in Restaurant(id={})".format(menu_id, restaurant_id)

@app.route("/restaurant//menus")
def menus(restaurant_id):
    restaurant = session.query(Restaurant).filter_by(id=restaurant_id).first()
    
    if restaurant:
        menus = session.query(MenuItem).filter_by(restaurant_id=restaurant_id).all()
        return flask.render_template('menu.html', items=menus, restaurant=restaurant)
    return "you come to a wrong page!"

if __name__ == '__main__':
    app.debug = True
    app.run(host='0.0.0.0', port=8080)

Form Requests and Redirects 表单提交和跳转

常用的三个函数

from flask import url_for, redirect, request

url_for 用于与响应函数绑定
redirect用于重定向
request用于获取form表单中的值

import flask
from flask import Flask, url_for, redirect, request
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
from database_setup import Base, Restaurant, MenuItem

app = Flask(__name__)

engine = create_engine('sqlite:///restaurantmenu.db')
Base.metadata.bind = engine

DBSession = sessionmaker(bind=engine)
session = DBSession()


@app.route('/')
@app.route('/hello')
def HelloWorld():
    restaurant = session.query(Restaurant).first()
    items = session.query(MenuItem).filter_by(restaurant_id=restaurant.id)
    output = ''
    for i in items:
        output += i.name
        output += '
'
        output += i.price
        output += '
'
        output += i.description
        output += '
'
        output += '
'
    return output

@app.route("/restaurant//new")
def new_menu_item(restaurant_id):
    return "create new menu item for the Restaurant(id={})".format(restaurant_id)

@app.route("/restaurant//edit/", methods=['GET', 'POST'])
def edit_menu_item(restaurant_id, menu_id):
    menu = session.query(MenuItem).filter_by(id=menu_id).first()

    if request.method == 'POST':
        if request.form['name']:
            menu.name = request.form['name']
            session.add(menu)
            session.commit()
        return redirect(url_for('menus', restaurant_id=restaurant_id))
    else:
        return flask.render_template('editmenu.html', item=menu)

@app.route("/restaurant//delete/")
def delete_menu_item(restaurant_id, menu_id):
    return "delete the Menu(id={}) in Restaurant(id={})".format(menu_id, restaurant_id)

@app.route("/restaurant//menus")
def menus(restaurant_id):
    restaurant = session.query(Restaurant).filter_by(id=restaurant_id).first()
    
    if restaurant:
        menus = session.query(MenuItem).filter_by(restaurant_id=restaurant_id).all()
        return flask.render_template('menu.html', items=menus, restaurant=restaurant)
    return "you come to a wrong page!"

if __name__ == '__main__':
    app.debug = True
    app.run(host='0.0.0.0', port=8080)

message flashing

message flashing 用于与用户进行交互，反映用户操作产生的结果。

from flask import flash

app.secret_key = ‘super_secret_key’ 用来创建用户相关的会话（session）事务

from crypt import methods
import flask
from flask import Flask, url_for, redirect, request, flash
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
from database_setup import Base, Restaurant, MenuItem

app = Flask(__name__)

engine = create_engine('sqlite:///restaurantmenu.db')
Base.metadata.bind = engine

DBSession = sessionmaker(bind=engine)
session = DBSession()


@app.route('/')
@app.route('/hello')
def HelloWorld():
    restaurant = session.query(Restaurant).first()
    items = session.query(MenuItem).filter_by(restaurant_id=restaurant.id)
    output = ''
    for i in items:
        output += i.name
        output += '
'
        output += i.price
        output += '
'
        output += i.description
        output += '
'
        output += '
'
    return output

@app.route("/restaurant//new", methods=['GET', 'POST'])
def new_menu_item(restaurant_id):
    restaurant = session.query(Restaurant).filter_by(id=restaurant_id).first()
    if restaurant:
        if request.method == 'GET':
            return flask.render_template('createmenuitem.html', restaurant=restaurant)
        
        else:
            menu_item_name = request.form['name']
            if menu_item_name:
                session.add(MenuItem(name=menu_item_name, restaurant_id=restaurant_id))
                session.commit()
                flash("successfully created a new Menu Item!")
            return redirect(url_for('menus', restaurant_id=restaurant_id))
    return "you come to a wrong page"

@app.route("/restaurant//edit/", methods=['GET', 'POST'])
def edit_menu_item(restaurant_id, menu_id):
    menu = session.query(MenuItem).filter_by(id=menu_id).first()

    if request.method == 'POST':
        if request.form['name']:
            menu.name = request.form['name']
            session.add(menu)
            session.commit()
            flash("one Menu item has been editted")
        return redirect(url_for('menus', restaurant_id=restaurant_id))
    else:
        return flask.render_template('editmenu.html', item=menu)

@app.route("/restaurant//delete/", methods=['GET','POST'])
def delete_menu_item(restaurant_id, menu_id):
    menu = session.query(MenuItem).filter_by(id=menu_id).first()
    if menu:
        if request.method == 'POST':
            session.delete(menu)
            session.commit()
            flash("one menu item has been deleted")
        else:
            return flask.render_template('deletemenu.html', item=menu)
    return redirect(url_for('menus', restaurant_id=restaurant_id))

@app.route("/restaurant//menus")
def menus(restaurant_id):
    restaurant = session.query(Restaurant).filter_by(id=restaurant_id).first()
    
    if restaurant:
        menus = session.query(MenuItem).filter_by(restaurant_id=restaurant_id).all()
        return flask.render_template('menu.html', items=menus, restaurant=restaurant)
    return "you come to a wrong page!"

if __name__ == '__main__':
    app.secret_key = 'super_secret_key' # flash 
    app.debug = True
    app.run(host='0.0.0.0', port=8080)

对象序列化便于传递数据

class MenuItem(Base):
    __tablename__ = 'menu_item'
    name =Column(String(80), nullable = False)
    id = Column(Integer, primary_key = True)
    description = Column(String(250))
    price = Column(String(8))
    course = Column(String(250))
    restaurant_id = Column(Integer,ForeignKey('restaurant.id'))
    restaurant = relationship(Restaurant) 

#We added this serialize function to be able to send JSON objects in a serializable format
    @property
    def serialize(self):
       return {
           'name'         : self.name,
           'description'  : self.description,
           'id'           : self.id,
           'price'        : self.price,
           'course'       : self.course,
       }

from flask import jsonify

上面的函数serialize将被jsonify调用进行对象序列化

@app.route('/restaurants//menu/JSON')
def restaurantMenuJSON(restaurant_id):
    restaurant = session.query(Restaurant).filter_by(id=restaurant_id).one()
    items = session.query(MenuItem).filter_by(
        restaurant_id=restaurant_id).all()
    return jsonify(MenuItems=[i.serialize for i in items])