python3 flask 使用Mysql数据库

python3 flask 使用Mysql数据库

1. 创建flask基本项目结构

   from flask import Flask
   app = Flask(__name__)

2. 安装flask-sqlalchemy

   pip install flask-sqlalchemy

3. 导入配置

   from flask_sqlalchemy import SQLAlchemy
   
   app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql+pymysql://root:root@localhost/hhh'
   app.config['SQLALCHEMY_COMMIT_ON_TEARDOWN'] = True
   app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = True
   db = SQLAlchemy(app)

   python3 不再支持MySQKdb,连接mysql数据库需要使用pymysql

   安装pymysql

   pip install pymysql

4. 定义表模型

   class User(db.Model):
       id = db.Column(db.Integer, primary_key=True)
       username = db.Column(db.String(64), unique=True, nullable=True)
   
       def __init__(self, username):
           self.username = username
   
       def __repr__(self):
           return ''.format(self.username)

5. 创建表
   在python shell中

   >>> from app import db
   >>> db.create_all()

6. 添加数据
   在python shell中

   >>> from app import db
   >>> from app import User
   >>> user=User('hou')
   >>> db.session.add(user)
   >>> db.session.commit()

7. 查询数据库

   >>> User.query.all()
   []
   >>> User.query.filter_by(username='hou').first()
   

8. 一对多或一对一表关联

   • 定义Post 表模型

     from datetime import datetime
     class Post(db.Model):
      id = db.Column(db.Integer, primary_key=True)
      body = db.Column(db.Text)
      timestamp = db.Column(db.DateTime, index=True, default=datetime.utcnow)
      # 添加外键声明
      user_id = db.Column(db.Integer, db.ForeignKey('user.id'))
      def __repr__(self):
          return ''.format(self.body)

   • User添加关系

     class User(db.Model):
      id = db.Column(db.Integer, primary_key=True)
      username = db.Column(db.String(64), unique=True, nullable=True)
      # 新加的
      # 如果您想要一对一关系，您可以把 uselist=False 传给 relationship() 。
      posts = db.relationship('Post', backref='user', lazy='dynamic')
      def __init__(self, username):
          self.username = username
      def __repr__(self):
          return ''.format(self.username)

   • 执行创建表

   • 添加数据

     >>> from app import *
     >>> user=User.query.filter_by(username='hou').first()
     >>> post1=Post(body='post1post1post1post1post1post1',user=user)
     >>> db.session.add(post1)
     >>> db.session.commit()

   • 查询数据

     >>> user=User.query.filter_by(username='hou').first()
     >>> user.posts.all()
     [, ]
     >>> user.posts.filter_by(id=4).first()
     

9. 多对多表关联

   • 定义Category 表模型

     class Category(db.Model):
      id = db.Column(db.Integer, primary_key=True)
      name = db.Column(db.String(50))
      def __init__(self, name):
          self.name = name
      def __repr__(self):
          return '' % self.name

   • 定义关联表

     categorys = db.Table('categorys',
                       db.Column('id', db.Integer, primary_key=True),
                       db.Column('post_id', db.Integer, db.ForeignKey('post.id')),
                       db.Column('category_id', db.Integer, db.ForeignKey('category.id'))
                       )

   • Post 中添加关系

     categorys = db.relationship('Category', secondary=categorys, backref=db.backref('posts', lazy='dynamic'))

   • 执行创建表

   • 准备类别数据

     >>> from app import *
     >>> category1=Category(name="前端")
     >>> category2=Category(name="nodejs")
     >>> category3=Category(name="python")
     >>> db.session.add(category1)
     >>> db.session.add(category2)
     >>> db.session.add(category3)
     >>> db.session.commit()

   • 添加post

     >>> from app import *
     >>> category1=Category.query.get(1)
     >>> category2=Category.query.get(2)
     >>> category3=Category.query.get(3)
     >>> user=User.query.get(1)
     >>> post1=Post(body='关联的post',user=user,categorys=[category1])
     >>> post2=Post(body='关联的post',user=user,categorys=[category1,category2,category3])
     >>> db.session.add(post1)
     >>> db.session.add(post2)
     >>> db.session.commit()

10. 修改代码结构使其更好的提供接口

11. 提供简单rest接口user

    from flask import jsonify, request
    from app.api import bp
    
    from app.models import User
    from app import db
    from app.error import bad_request
    
    
    @bp.route('/users', methods=['GET'])
    def get_users():
        limit = min(request.args.get('limit', 10, int), 100)
        offset = (request.args.get('page', 1, int) - 1) * request.args.get('limit', 10, int)
        return jsonify([user.to_dict() for user in User.query.limit(limit).offset(offset).all()])
    
    
    @bp.route('/users/', methods=['GET'])
    def get_user(id):
        return jsonify(User.query.get_or_404(id).to_dict())
    
    
    @bp.route('/users', methods=['POST'])
    def add_user():
        data = request.get_json() or {}
        if 'username' not in data:
            return bad_request('错误的参数')
        user = User(username=data['username'])
        db.session.add(user)
        db.session.commit()
        return jsonify(user.to_dict())
    
    
    @bp.route('/users/', methods=['PUT'])
    def update_user(id):
        user = User.query.get_or_404(id)
        data = request.get_json() or {}
        if 'username' not in data:
            return bad_request('错误的参数')
        setattr(user, 'username', data['username'])
        db.session.commit()
        return jsonify(user.to_dict())
    
    
    @bp.route('/users/', methods=['DELETE'])
    def delete_user(id):
        user = User.query.get_or_404(id)
        db.session.delete(user)
        db.session.commit()
        return jsonify({'message': 'ok'})
    

12. 源代码地址 https://github.com/houxiaozhao/python3-flask-mysql