Flask-SQLAlchemy 使用起來非常有趣，對於基本應用十分容易使用，並且對於大型專案易於擴充套件。
官方文件：https://flask-sqlalchemy.palletsprojects.com/en/2.x/
中文文件：http://www.pythondoc.com/flask-sqlalchemy/

安裝

pip install flask-sqlalchemy

配置

建立及查詢

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
app = Flask(name)

app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:////tmp/test.db'

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)

<span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">__init__</span>(<span class="hljs-params">self, username, email</span>):</span>
    self.username = username
    self.email = email

<span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">__repr__</span>(<span class="hljs-params">self</span>):</span>
    <span class="hljs-keyword">return</span> <span class="hljs-string">'&lt;User %r&gt;'</span> % self.username

if name == 'main':

# 建立初始資料

db.create_all()

# 建立一些使用者

admin = User('admin', '[email protected]')

guest = User('guest', '[email protected]')

# 寫入到資料庫

db.session.add(admin)

db.session.add(guest)

db.session.commit()

# 訪問資料庫

users = User.query.all()

admin = User.query.filter_by(username='admin').first()

print(users)

print(admin)

結果：

[<User 'admin'>, <User 'guest'>]
<User 'admin'>

表關聯

SQLAlchemy 連線到關係型資料庫，關係型資料最擅長的東西就是關聯。因此，我們將建立一個使用兩張相互關聯的表的應用作為例子:

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from datetime import datetime
app = Flask(name)

app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:////tmp/test.db'

db = SQLAlchemy(app)
class Post(db.Model):

id = db.Column(db.Integer, primary_key=True)

title = db.Column(db.String(80), nullable=False)

body = db.Column(db.Text, nullable=False)

pub_date = db.Column(db.DateTime, nullable=False,

default=datetime.utcnow)
category_id = db.Column(db.Integer, db.ForeignKey(<span class="hljs-string">'category.id'</span>), <span class="hljs-comment"># 外來鍵</span>
                        nullable=<span class="hljs-literal">False</span>)

<span class="hljs-comment"># 與生成表結構無關，僅用於查詢方便</span>
<span class="hljs-comment"># backref 標示可通過relationship反向查詢，Category.posts查詢Post表資料</span>
category = db.relationship(<span class="hljs-string">'Category'</span>,
                           backref=db.backref(<span class="hljs-string">'posts'</span>, lazy=<span class="hljs-literal">True</span>))

<span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">__repr__</span>(<span class="hljs-params">self</span>):</span>
    <span class="hljs-keyword">return</span> <span class="hljs-string">'&lt;Post %r&gt;'</span> % self.title

class Category(db.Model):

id = db.Column(db.Integer, primary_key=True)

name = db.Column(db.String(50), nullable=False)
<span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">__repr__</span>(<span class="hljs-params">self</span>):</span>
    <span class="hljs-keyword">return</span> <span class="hljs-string">'&lt;Category %r&gt;'</span> % self.name

if name == 'main':

# 建立一些物件

py = Category(name='Python')

Post(title='Hello Python!', body='Python is pretty cool', category=py)

p = Post(title='Snakes', body='Ssssssss')

py.posts.append(p)

db.session.add(py)
<span class="hljs-comment"># 現在因為我們在 backref 中聲明瞭 posts 作為動態關係，查詢顯示為:</span>
print(py.posts)

執行結果：

[<Post 'Hello Python!'>, <Post 'Snakes'>]

更多資料庫的增刪改查等功能參考官方文件：https://flask-sqlalchemy.palletsprojects.com/en/2.x/queries/