轻量级Web框架Flask（二）

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## Summary of the Python code: This code defines a Flask application with a focus on book management. It handles user authentication, displays a login form, and allows authorized users to view and manage books. **Key features:** * **Models:** * `User`: Stores user information (username, password, email). * `Book`: Stores book information (id, title, author, etc.). * **Views:** * `index`: Handles user login and displays the main page. * `login`: Shows the login form. * `register`: Handles user registration. * **Template:** * `login.html`: The login page template. * `index.html`: The main page template displaying book information. * **Database:** * The application uses a SQLite database for data persistence. * Data models are defined using SQLAlchemy. * Foreign key relationships are established between `User` and `Book` models. ## Code breakdown: **app.py:** * Creates an instance of the Flask application. * Configures the application and database. * Registering blueprint(s) for admin, common, and front-end functionality. * Setting up database connection and creating tables. **models.py:** * Defines the `User` and `Book` models using SQLAlchemy. * The `Book` model defines a foreign key relationship with the `User` model. **views.py:** * Defines a `index` view for the main page. * Uses a `NameForm` to handle login submissions. * Validates the form and displays appropriate messages. * Renders the `login.html` template if authentication fails. **templates/login.html:** * Shows the login form with required fields. * Provides a token and error message for successful and failed login attempts. **exts.py:** * Provides a `SQLAlchemy` instance for database interaction. * Uses the `SQLAlchemy` instance to perform database operations. **Overall, this code demonstrates a complete Flask application with proper model and view separation, using SQLAlchemy for database management and providing a clean and modular design.**

正文

Flask-SQLAlchemy

MySQL是免费开源软件，大家可以自行搜索其官网（https://www.MySQL.com/downloads/）

测试MySQL是否安装成功

在所有程序中，找到MySQL→MySQL Server 5.6下面的命令行工具，然后单击输入密码后回车，就可以知道MySQL数据库是否链接成功。

右击桌面上的“计算机”，在弹出的快捷键菜单中选择“属性”｜“高级系统设置”｜“环境变量”，在path里面添加MySQL bin目录的路径。选择环境变量，在环境变量中的path路径下输入你的MySQL路径就行了。默认安装的路径是C:\MySQL\MySQL Server 5.6\bin

安装flask-sqlalchemy，安装不了就更换豆瓣源

pip install flask-sqlalchemy

对象-关系映射实质

class  Lib_card(db.Model):
    __tablename__ = 'lib_card'
    id = db.Column(db.Integer, primary_key=True, comment='id号')
    card_id = db.Column(db.Integer, nullable=False, comment = '借书证')
    book_id = db.Column(db.Integer, db.ForeignKey('book.id'))
    books = db.relationship('Book', backref=db.backref('cards'),uselist=False)

在Flask-SQLAlchemy中，插入、修改、删除操作均由数据库会话管理

需要一个配置config.py

USERNAME= 'root'                                        #设置登录账号
PASSWORD= '930103'                                        #设置登录密码
HOST= '127.0.0.1'                                        #设置主机地址
PORT= '3306'                                                #设置端口号
DATABASE= 'demo1'                                #设置访问的数据库
SQLALCHEMY_DATABASE_URI= f'mysql+pymysql://{USERNAME}:{PASSWORD}@{HOST}:{PORT}/{DATABASE}'#创建数据库连接示例
#动态追踪修改设置，如未设置只会提示警告
SQLALCHEMY_TRACK_MODIFICATIONS=False
#查询时会显示原始SQL语句
SQLALCHEMY_ECHO= True

实例

from datetime import datetime

from flask import Flask                                                        #导入Flask模块
from flask_sqlalchemy import SQLAlchemy               #导入SQLAlchemy模块
import config                                                                 #导入配置文件
app= Flask(__name__)                                                        #Flask初始化
app.config.from_object(config)                                        #配置文件实例化
#初始化一个对象
db=SQLAlchemy(app)

class Book(db.Model):
    __tablename__ = 'book'
    id = db.Column(db.Integer, primary_key = True,comment='id号')
    title = db.Column(db.String(50), nullable=False,comment='书名')
    publishing_office = db.Column(db.String(100), nullable=False,comment='出版社')
    isbn = db.Column(db.String(100), nullable=False, comment='isbn号')
    storage_time = db.Column(db.DateTime, default=datetime.now(), comment='入库时间')

class  Lib_card(db.Model):
    __tablename__ = 'lib_card'
    id = db.Column(db.Integer, primary_key=True, comment='id号')
    card_id = db.Column(db.Integer, nullable=False, comment = '借书证')
    book_id = db.Column(db.Integer, db.ForeignKey('book.id'))
    books = db.relationship('Book', backref=db.backref('cards'),uselist=False)

with app.app_context():
#测试数据库连接是否成功
    db.create_all()     #创建数据库
    # book1= Book(id=9,title='智能导论', publishing_office='高等教育出版社',isbn='9787040479844')
    # db.session.add(book1)
    # db.session.commit()
    # result = Book.query.filter(Book.id == 9).first()
    # print(result.title)
    # agine = Book.query.filter(Book.title == result.title).all()
    # for i in agine:
    #     print(i.id)
    # db.session.delete(result)
    # db.session.commit()
    # card1=Lib_card(card_id='18001', book_id='8')
    # card2=Lib_card(card_id='18002', book_id='8')
    # db.session.add(card1)
    # db.session.add(card2)
    # db.session.commit()
    book_query = Book.query.filter(Book.id == 9).first()
    lib_card_query = book_query.cards
    for i in lib_card_query:
        print(i.card_id)

@app.route('/')
def index():
    return 'index'

# if __name__== '__main__':
#     app.run(debug=True)

注意：一个表（模型）的定义必须要定义一个主键，这个主键一般为id。在定义了Lib_card类后，申明了一个外键，并且在relationship方法中使用uselist=False来约束其关系。book_id =db.Column(db.Integer,db.ForeignKey('book.id'))表示创建一个外键，类型要跟主表一样，通过db.ForeignKey("user.id")与主表绑定books =db.relationship('Book'，backref=db.backref('cards')；uselist=False)表示Book可以根据Lib_card中的借书证查找到book表中的信息,backref="cards"表示book表可以直接通过cards查找到该书下的借书证号码。

框架实例

建一个apps文件夹，添加一个admin包，admin包下创建三个py文件

#__init__.py
#预加载模块内容
#其他地方调用的时候 可以直接from apps.admin import bp as admin_bp不用找到views
from .views import bp

#forms.py
from flask_wtf import FlaskForm
from wtforms import *
from wtforms.validators import *

class NameForm(FlaskForm):
    username = StringField('用户名',validators=[DataRequired()])
    password = PasswordField('密码',validators=[DataRequired()])
    submit = SubmitField('提交')

#models.py
from exts import db

class User(db.Model):
    __tablename__ = 'jq_user'
    uid = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(50), nullable=False, comment="用户名")
    password = db.Column(db.String(100), nullable=False,comment="密码")
    email = db.Column(db.String(50), nullable=False, unique=True, comment = "邮箱")

#views.py
from flask import Blueprint, request, flash, render_template
from apps.admin.forms import NameForm
from apps.admin.models import User

bp = Blueprint("admin",__name__)

@bp.route("/admin",methods=['GET','POST'])
def index():
    form = NameForm()
    if request.method == 'POST':
        if form.validate_on_submit():
            username = request.form.get('username')
            password = request.form.get('password')
            result = User.query.filter(User.username==username).first()
            if result and password == result.password:
                flash('登录成功')
            else:
                return render_template('login.html', form=form, errormsg="登陆失败")
    return render_template('login.html', form=form)

建一个文件夹templates，专门放login.html文件，通过render_template调用

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <h1>用户注册登录</h1>
    <form method="post" action="/test/admin">
        {{ form.csrf_token()}}
        {{ form.username.label }}{{ form.username}}
        {{ form.password.label }}{{ form.password}}
        {{ form.submit }}{{errormsg}}

        {% for message in get_flashed_messages() %}
            {{ message }}
        {% endfor %}
    </form>
</head>
<body>

</body>
</html>

建一个app.py

from flask import Flask
from apps.admin import bp as admin_bp
from exts import db
from apps.common import bp as common_bp
from apps.front import bp as front_bp
from apps.admin.models import User
from apps.common.models import Book


def create_app():
    app = Flask(__name__)
    app.secret_key = '123321'
    #注册蓝图,注册时候可以设置前缀
    app.register_blueprint(admin_bp,url_prefix="/test")
    app.register_blueprint(common_bp)
    app.register_blueprint(front_bp)
    app.config.from_object('config')
    # db.app = app
    db.init_app(app)
    return app



if __name__ == '__main__':
    app = create_app()
    with app.app_context():
        db.create_all()
    app.run(host="127.0.0.1",port=1314,debug=True)

建一个config.py

DEBUG=True
USERNAME= 'root'                                        #设置登录账号
PASSWORD= '930103'                                        #设置登录密码
HOST= '127.0.0.1'                                        #设置主机地址
PORT= '3306'                                                #设置端口号
DATABASE= 'demo1'                                #设置访问的数据库
SQLALCHEMY_DATABASE_URI= f'mysql+pymysql://{USERNAME}:{PASSWORD}@{HOST}:{PORT}/{DATABASE}'#创建数据库连接示例
#动态追踪修改设置，如未设置只会提示警告
SQLALCHEMY_TRACK_MODIFICATIONS=False
#查询时会显示原始SQL语句
SQLALCHEMY_ECHO= True

建一个exts.py

#encoding:utf-8
from flask_sqlalchemy import SQLAlchemy
db=SQLAlchemy()