• flask 中的ORM ( 二 )


    1 关系映射
        1 多对多
            1 什么是多对多
                A表中的一条数据可以与B表中任意多条数据相关联
                B表中的一条数据可以与A表中任意多条数据相关联
            2 实现
                在数据库中使用第三张表(关联表)
                在编程语言中,可以不编写对应的实体类
                1 创建第三张表
                    student_course = db.Table(
                        'student_course',# 在数据库中的表名
                        db.Column('id',db.Integer,primary_key = True),
                        db.Column('student_id',db.Integer,db.ForeignKey('student.id')),
                        db.Column('course_id,db.Integer,db.ForeignKey('course.id'))
                    )

    from flask import Flask,render_template,request
    from flask_sqlalchemy import SQLAlchemy
    
    app = Flask(__name__)
    db = SQLAlchemy(app)
    app.config['SQLALCHEMY_DATABASE_URI']= 'mysql+pymysql://root:liu@176.215.155.241:3306/flask' # 创建连接实例
    app.config['SQLALCHEMY_COMMIT_ON_TEARDOWN'] = True   #自动提交
    
    class Course(db.Model):
        __tablename__='course'
        id = db.Column(db.Integer,primary_key=True)
        cname = db.Column(db.String(30),nullable=True)
        #增加关联属性和反向引用关系
        # 关联属性在course对象中通过哪个属性能够得到对应的所有的teacher
        #反向引用关系:在teacher对象中通过哪个属性能找到它对应的course
        teachers = db.relationship('Teacher',backref ='course',lazy ='dynamic')
    
        def __init__(self,name):
            self.cname=name
    
        def __repr__(self):
            return '<Coure:%r>'%self.cname
    
    class Teacher(db.Model):
        __tablename__='teacher'
        id = db.Column(db.Integer,primary_key=True)
        tname = db.Column(db.String(30),nullable=True)
        tage = db.Column(db.Integer)
        course_id = db.Column(db.Integer,db.ForeignKey('course.id'))
        # 增加关联属性以及反向引用
        student = db.relationship('Student',backref = 'teacher',lazy='subquery')
        wife = db.relationship('Wife',backref='teacher',uselist=False)
    
        def __init__(self,name,age,course_id):
            self.tname=name
            self.tage=age
            self.course_id=course_id
        def __repr__(self):
            return '<Teacher %r>'%self.name
    
    class Wife(db.Model):
        __tablename__='wife'
        id=db.Column(db.Integer,primary_key=True)
        wname =db.Column(db.String(30))
        wage = db.Column(db.Integer)
        #增加一个列(外键):表示引用自Teacher表的主键
        teacher_id = db.Column(db.Integer,db.ForeignKey('teacher.id'))
        def __init__(self,wname,wage):
            self.wname = wname
            self.wage = wage
    
        def __repr__(self):
            return '<Wife %r>'%self.wname
    
    class Student(db.Model):
        __tablename__='student'
        id = db.Column(db.Integer,primary_key=True)
        sname = db.Column(db.String(10))
        sage = db.Column(db.Integer)
        steacher = db.Column(db.Integer,db.ForeignKey('teacher.id'))
        courses = db.relationship('Course',
                                  secondary='student_course',
                                  lazy = 'dynamic',
                                  backref=db.backref('students', lazy='dynamic'))
        teachers = db.relationship('Teacher',secondary ='student_teacher',
                                   lazy = 'dynamic',
                                   backref = db.backref('teachers',lazy ='dynamic'))
        def __repr__(self):
            return '<student %s>'%self.sname
    
    student_course = db.Table(
        'student_course',
        db.Column('id',db.Integer,primary_key=True),
        db.Column('student_id',db.Integer,db.ForeignKey('student.id')),
        db.Column('course_id',db.Integer,db.ForeignKey('course.id'))
    )
    
    student_teacher = db.Table(
        'student_teacher',
        db.Column('id',db.Integer,primary_key=True),
        db.Column('student_id',db.Integer,db.ForeignKey('student.id')),
        db.Column('teacher_id',db.Integer,db.ForeignKey('teacher.id'))
    )
    
    db.create_all()
    
    
    @app.route('/')
    def hello_world():
        return 'Hello World!'
    
    @app.route('/01-addcourse')
    def add_course():
        course1 = Course('python基础')
        course2 = Course('python高级')
        course3 = Course('数据基础')
        db.session.add(course1)
        db.session.add(course2)
        db.session.add(course3)
        return '1'
    
    @app.route('/02-register')
    def register_teacher():
        teacher = Teacher()
        teacher.tname='吕老师'
        teacher.tage = 28
        course = Course.query.filter_by(id=3).first()
        # teacher.course = course #通过关联属性course对象赋值
        teacher.course_id = 1
        db.session.add(teacher)
        return '1'
    
    @app.route('/03-query-teacher')
    def query_teacher():
        # 通过 course 查找对应的所有的老师们
        # 查找course_id 为1的course对象
        # course = Course.query.filter_by(id=1).first()
        # print(course.cname)
        # for tea in course.teachers.all():
        #     print(tea.tname)
    
        #通过teacher 查找对应的course
        teacher = Teacher.query.filter_by(id=1).first()
        print('老师姓名',teacher.tname)
        course = teacher.course
        print(course.cname)
    
        pass
    
    @app.route('/04-regTeacher',methods=['GET','POST'])
    def reg_Teacher():
        if request.method=='GET':
            a = Course.query.all()
            return render_template('regTeacher.html',a=a)
    
        elif request.method=='POST':
            name = request.form['name']
            age = request.form['age']
            select = request.form['select1']
    
            db.session.add(Teacher(name,age,select))
            return '1'
    
    @app.route('/05-showdata')
    def showdata_05():
        a = Teacher.query.all()
        return render_template('showtea.html',a=a)
    
    @app.route('/06-regwife')
    def regwife():
        # wife = Wife('王dd夫人',18)
        # wife.teacher_id=1
        # db.session.add(wife)
    
        wife=Wife('老夫人',15)
        teacher = Teacher.query.filter_by(tname='刘杰').first()
        wife.teacher = teacher
        db.session.add(wife)
        return 'OK'
    
    @app.route('/07-querywife')
    def querywife():
        #通过teacher 找wife
        # teacher = Teacher.query.filter_by(id=1).first()
        # wife = teacher.wife
    
    
        # 通过wife找 teacher
        wife = Wife.query.filter_by(id=2).first()
        teacher = wife.teacher
        return '%s--%s'%(teacher.tname,wife.wname)
    
    @app.route('/07-get')
    def get_07():
        a= Teacher.query.filter_by(id =4).first()
        b = a.student
        c = a.wife
        print(b,c)
    
        return render_template('07-get.html',a=b)
    
    @app.route('/08')
    def add_student_course():
        # 获取id为1 的学员的信息
        student =Student.query.filter_by(id=1).first()
        # 获取 id为1 的课程信息
        course = Course.query.filter_by(id=1).first()
        # 将student 与 course 关联到一起
        student.courses.append(course)
    
        db.session.add(student)
    
        for i in student.courses:
            print(i)
        return '1'
    
    @app.route('/09')
    def getM2M():#这里是多对多存储关系
        courses = Course.query.filter_by(id=1).first()
        students = courses.students.all()
        print(students)
        return '1'
    
    @app.route('/10',methods=['GET','POST'])
    def register_student():
        if request.method=="GET":
            s = Student.query.all()
            t = Teacher.query.all()
            return render_template('register_student.html',s=s,t=t)
        elif request.method=='POST':
            studen = request.form['select1']
            teacher = request.form.getlist('select2')
            print(teacher)
            s = Student.query.filter_by(id=int(studen)).first()
            t = Teacher.query.filter(Teacher.id.in_(teacher)).all()
            for i in t :
                s.teachers.append(i)
            db.session.add(s)
    
            return 'OK'
    
    @app.route('/011')
    def show_011():
        s = Student.query.all()
        return render_template('show_11.html',s=s)
    
    if __name__ == '__main__':
        app.run(debug=True)
    View Code (内包含一对一,一对多,多对多的ORM实现)
    2 cookies / cookie 
        1 什么是cookies 
            cookie 是一种数据的存储手段
            将一段文本保存在客户端(浏览器)的一种手段,并可以长时间保存
        2 cookies的使用场合
            1 记住密码
            2 记住搜索的关键词
        3 Flask 中使用 cookies
            1 使用响应对象,将数据保存进cookies(客户端)
                1 resp = make_response('字符串'|rende_template())
                2 resp = redirect('地址')
                cookies的语法
                响应对象.set_cookies(key,value,max_age)
                    key:保存的cookie的名称
                    value:保存的cookie的值
                    max_age:保存的时间,取值为数字,默认以s 为单位
                        
            2 获取 cookie的值
                每次向服务器请求时,都会把cookie中的数据封装到request中并带到服务器上
                在flask中通过request.cookies 获取所有的cookies值
            3 删除cookie的值
                响应对象. delete_cookie('key')
    3 session - 会话
        1 什么是session
            session是保存在服务器上,为每个浏览器所开辟的一段空间
        2 session 在Flask 中的实现
            1 配置 SECRET_KEY
                app.config['SECRET_KEY'] = '123456'
            2 使用session
                from flask import session
                1 向session中保存数据
                    session['key'] = value
                2 从session中取值
                value = session['key']
                    value  = session.get('key','')
                3 从session中删除数据
                    del session['key']
                    
                
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  • 原文地址:https://www.cnblogs.com/Skyda/p/9909361.html
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