大白话说Python+Flask入门（六）Flask SQLAlchemy操作mysql数据库-526互联

写在前面

这篇文章被搁置真的太久了，不知不觉拖到了周三了，当然，也算跟falsk系列说再见的时候，真没什么好神秘的，就是个数据库操作，就大家都知道的CRUD吧。

Flask SQLAlchemy的使用

1、Flask SQLAlchemy简介

Flask SQLAlchemy 是基于 Flask web 框架和 SQLAlchemy ORM（对象关系映射）的工具。它旨在为 Flask web 应用程序提供更方便的数据库操作。SQLAlchemy 本身是一个全功能的 ORM，而 Flask-SQLAlchemy 是在此基础上为 Flask 应用程序提供了一些额外的功能。

2、安装Flask-SQLAlchemy

pip install flask-sqlalchemy

3、举个栗子

后端业务代码如下：

import pymysql
from flask import Flask, request, flash, url_for, redirect, render_template
from flask_sqlalchemy import SQLAlchemy

from flask_case.config import Config

pymysql.install_as_MySQLdb()

# 实例化一个flask对象
app = Flask(__name__)
# 设置一个密钥
app.secret_key = 'a_secret_key'
# 从配置对象中加载配置信息
app.config.from_object(Config)
# 创建SQLAlchemy对象
db = SQLAlchemy(app)

class books(db.Model):
    id = db.Column('student_id', db.Integer, primary_key=True)
    name = db.Column(db.String(100))
    price = db.Column(db.String(50))

    def __init__(self, name, price):
        self.name = name
        self.price = price





@app.route('/')
def show_all():
    return render_template('show_all.html', books=books.query.all())


@app.route('/add', methods=['GET', 'POST'])
def add():
    if request.method == 'POST':
        if not request.form['name'] or not request.form['price']:
            flash('输入项不能为空！', 'error')
        else:
            book = books(request.form['name'], request.form['price'])
            print(book)
            db.session.add(book)
            db.session.commit()
            flash('新书上架成功！')
            return redirect(url_for('show_all'))
    return render_template('add.html')


if __name__ == '__main__':
    with app.app_context():
        db.create_all()
    app.run(debug=True)

新增书页面add.html，示例代码如下：

<!DOCTYPE html>
<html>
   <body>

      <h3>Flask SQLAlchemy Demo</h3>
      <hr/>

      {%- for category, message in get_flashed_messages(with_categories = true) %}
         <div class = "alert alert-danger">
            {{ message }}
         </div>
      {%- endfor %}

      <form action = "{{ request.path }}" method = "post">
         <label for = "name">name</label><br>
         <input type = "text" name = "name" placeholder = "name" /><br>
         <label for = "price">price</label><br>
         <input type = "text" name = "price" placeholder = "price" /><br>
         <input type = "submit" value = "Submit" />
      </form>

   </body>
</html>

书单列表页show_all.html，示例代码如下：

<!DOCTYPE html>
<html lang = "en">
   <head></head>
   <body>
      
      <h3>
         <a href = "{{ url_for('show_all') }}">Flask
            SQLAlchemy Demo</a>
      </h3>
      
      <hr/>
      {%- for message in get_flashed_messages() %}
         {{ message }}
      {%- endfor %}
       
      <h3>Books (<a href = "{{ url_for('add') }}">Add Book
         </a>)</h3>
      
      <table>
         <thead>
            <tr>
               <th>name</th>
               <th>price</th>
            </tr>
         </thead>
         
         <tbody>
            {% for book in books %}
               <tr>
                  <td>{{ book.name }}</td>
                  <td>{{ book.price }}</td>
               </tr>
            {% endfor %}
         </tbody>
      </table>
      
   </body>
</html>