python3 flask 使用 Mysql 数据库

创建 flask 基本项目结构

1 2	from flask import Flask app = Flask(__name__)

安装flask-sqlalchemy
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pip install flask-sqlalchemy

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

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 '<User {}>'.format(self.username)

创建表
在 python shell 中

1 2	>>> from app import db >>> db.create_all()

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()

查询数据库

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

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 '<Post {}>'.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 '<User {}>'.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()
[<Post 哈哈哈哈哈>, <Post post1post1post1post1post1post1>]
>>> user.posts.filter_by(id=4).first()
<Post post1post1post1post1post1post1>

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 '<Category %r>' % 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

1	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()

修改代码结构使其更好的提供接口

提供简单 rest 接口user
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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/int:id‘, 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/int:id‘, 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/int:id‘, methods=[‘DELETE’])
def delete_user(id):
user = User.query.get_or_404(id)
db.session.delete(user)
db.session.commit()
return jsonify({‘message’: ‘ok’})
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源代码地址 https://github.com/houxiaozhao/python3-flask-mysql