pip install flask-sqlalchemy pymysql 

from flask.ext.sqlalchemy import SQLAlchemy 
from flask import Flask 
 
'''配置数据库'''
app = Flask(__name__) 
app.config['SECRET_KEY'] ='hard to guess'
# 这里登陆的是root用户，要填上自己的密码，MySQL的默认端口是3306，填上之前创建的数据库名jianshu,连接方式参考 \ 
# http://docs.sqlalchemy.org/en/latest/dialects/mysql.html 
app.config['SQLALCHEMY_DATABASE_URI']='mysql+pymysql://jianshu:jianshu@127.0.0.1:3306/jianshu'
#设置这一项是每次请求结束后都会自动提交数据库中的变动 
app.config['SQLALCHEMY_COMMIT_ON_TEARDOWN']=True
#实例化 
db = SQLAlchemy(app)

'''定义模型，建立关系'''
class Role(db.Model): 
 # 定义表名 
 __tablename__ = 'roles'
 # 定义列对象 
 id = db.Column(db.Integer, primary_key=True) 
 name = db.Column(db.String(64), unique=True) 
 user = db.relationship('User', backref='role') 
 
 #repr()方法显示一个可读字符串，虽然不是完全必要，不过用于调试和测试还是很不错的。 
 def __repr__(self): 
  return '<Role {}> '.format(self.name) 
 
class User(db.Model): 
 __tablename__ = 'users'
 id = db.Column(db.Integer, primary_key=True) 
 username = db.Column(db.String(64), unique=True, index=True) 
 role_id = db.Column(db.Integer, db.ForeignKey('roles.id')) 
 
 def __repr__(self): 
  return '<User {}>'.format(self.username)

class Role(db.Model): 
 # ... 
 users = db.relationship('User', backref='role') 
 
class User(db.Model): 
 # ... 
 role_id = db.Column(db.Integer, db.ForeignKey('roles.id')) 

#!/usr/bin/env python 
 
from exts import db 
from datetime import datetime 
 
 
class User(db.Model): 
 __tablename__ = 'user'
 id = db.Column(db.Integer,primary_key=True,autoincrement=True) 
 username = db.Column(db.String(50),nullable=False) 
 telephone = db.Column(db.String(11),nullable=False) 
 password = db.Column(db.String(100), nullable=False) 
 
class Questions(db.Model): 
 __tablename__ = 'questions'
 id = db.Column(db.Integer,primary_key=True,autoincrement=True) 
 title = db.Column(db.String(100),nullable=False) 
 content = db.Column(db.Text,nullable=False) 
 create_time = db.Column(db.DateTime,default=datetime.now) 
 author_id = db.Column(db.Integer,db.ForeignKey('user.id')) 
 
 author = db.relationship('User',backref=db.backref('questions')) 
 
class Answer(db.Model): 
 __tablename__ = 'answer'
 id = db.Column(db.Integer,primary_key=True,autoincrement=True) 
 content = db.Column(db.Text,nullable=False) 
 question_id = db.Column(db.Integer,db.ForeignKey('questions.id')) 
 author_id = db.Column(db.Integer,db.ForeignKey('user.id')) 
 
 question = db.relationship('Questions',backref = db.backref('answers')) 
 author = db.relationship('User',backref = db.backref('answers'))