flask开发之flask-SQLAlchemy

flask不像django，django有自己的ORM集成实现。flask一般使用sqlalchemy进行集成开发，网上已有flask-sqlchrmy可以直接使用。下面来个入门demo。
安装flask、flask-SQLAlchemy

pip install flask
pip install flask-SQLAlchemy

建立三个表的ORM对象，分别是user、post、category。
其中post与category有外键关联。

import datetime
from flask import Flask
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///tmp/test.db'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
db = SQLAlchemy(app)

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(80), unique=True)
    email = db.Column(db.String(120), unique=True)

    def __init__(self, username, email):
        self.username = username
        self.email = email

    def __repr__(self):
        return '<User %r>' % self.username

class Post(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    title = db.Column(db.String(80))
    body = db.Column(db.Text)
    pub_date = db.Column(db.DateTime)

    category_id = db.Column(db.Integer, db.ForeignKey('category.id'))
    category = db.relationship('Category', backref=db.backref('posts', lazy='dynamic'))

    def __init__(self, title, body, category, pub_date=None):
        self.title = title
        self.body = body
        if pub_date is None:
            pub_date = datetime.datetime.utcnow()
        self.pub_date = pub_date
        self.category = category

    def __repr__(self):
        return '<Post %r>' % self.title

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

一些基本操作

from demo import db, User, Category, Post

#创建数据库与表
db.create_all()

#创建User对象并插入数据库
admin = User('admin', 'admin@example.com')
guest = User('guest', 'guest@example.com')
db.session.add(admin)
db.session.add(guest)
db.session.commit()

#查询
users = User.query.all()
admin = User.query.filter_by(username='admin').first()

#创建Post与Category并插入数据库
py = Category('python')
p = Post('Hello python!', 'pytho is pretty cool', py)
db.session.add(py)
db.session.add(p)
db.session.commit()

参考链接：
http://flask-sqlalchemy.pocoo.org/2.3/quickstart/#a-minimal-application