Flask -SQLAlchemy 数据库一对一

from  flask import Flask
from flask_sqlalchemy import SQLAlchemy
from datetime import datetime
import config
app = Flask(__name__)
app.config.from_object(config)
db = SQLAlchemy(app)
class User(db.Model):
    __tablename__ = "user"
    id  = db.Column(db.Integer,primary_key=True,autoincrement=True)
    username = db.Column(db.String(50),nullable=False)
    password = db.Column(db.String(50),nullable=False)
    phone = db.Column(db.String(11),nullable=False)
    email = db.Column(db.String(30),nullable=False)
    reg_time = db.Column(db.DateTime,default = datetime.now)
class Lib_card(db.Model):
    __tablename__ ='lib_card'
    id = db.Column(db.Integer,primary_key=True,autoincrement=True)
    card_id = db.Column(db.Integer,nullable=False)
    papers_type = db.Column(db.String(50),nullable=False)
    borrow_reg_time = db.Column(db.DateTime,default=datetime.now)
    user_id = db.Column(db.Integer,db.ForeignKey('user.id'))
    users = db.relationship('User',backref=db.backref('cards'),uselist=False)
db.create_all()
@app.route('/add')
def add():
    user1 = User(username='张三',password='1111111',phone='138888888',email='10086@qq.com')
    user2 = User(username='李氏',password='2222222',phone='137777777',email='10000@qq.com')
    db.session.add(user1)
    db.session.add(user2)

    card1 = Lib_card(card_id='18001',user_id='1',papers_type='身份证')
    card2= Lib_card(card_id='18002',user_id='2',papers_type='身份证')
    db.session.add(card1)
    db.session.add(card2)
    db.session.commit()
    return '添加数据成功'
@app.route('/select')
def select():
    user = User.query.filter(User.username=='张三').first()
    art = user.cards
    for k in art:
        print(k)
        print(k.card_id)
    card = Lib_card.query.filter(Lib_card.card_id=='18001').first()
    user = card.users
    print(user.username)
    return '查询数据成功'


@app.route('/')
def index():
    return 'index'
if __name__ == '__main__':
    app.run(debug=True)

config 为数据库链接配置

USERNAME = 'root'
PASSWD='1234qwer￥%&'
HOST='127.0.0.1'
PORT='3306'
DATABASE='db_demo1'
DB_URI="mysql+pymysql://{}:{}@{}:{}/{}?charset=utf8".format(USERNAME,PASSWD,HOST,PORT,DATABASE)
SQLALCHEMY_DATABASE_URI=DB_URI
SQLALCHEMY_TRACK_MODIFICATIONS=False
SQLALCHEMY_ECHO = True