《Flask web开发》笔记4：数据库

Posted 2020-10-05

一、实现功能：通过web表单生成登录界面、当输入的用户名不在后台数据库里时，加进去；在时，显示Happy see you again样式；

      1.数据库引擎：mysql （安装没有要求路径，我是用之前的没动）

      2.数据库框架： Flask-SQLAlchemy（书上推荐，直接pip install  Flask-SQLAlchemy 就行）

      

二、 Flask-SQLAlchemy建一个简单的表：

 

      aa.py：

# coding: utf-8
from flask import Flask
from flask_script import Manager
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config[‘SQLALCHEMY_DATABASE_URI‘] = ‘mysql://[email protected]/yxctest‘       #MySQL数据库UILmysql://username:[email protected]/database
app.config[‘SQLALCHEMY_COMMIT_ON_TEARDOWN‘] = True#实时更新

db = SQLAlchemy(app)  #实例化db
manager = Manager(app)

class User(db.Model):
    __tablename__ = ‘users‘    #表名
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(80), unique=True)
    email = db.Column(db.String(320), unique=True)
    password = db.Column(db.String(32), nullable=False)

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

if __name__ == ‘__main__‘:
    manager.run()

然后在doc输入 Python aa.py shell

接着就可以对这个表进行操作了：

           from aa import db、from aa import User、db.create_all()、user1 = User(username = ‘yxc‘,email=‘[email protected]‘,password=‘123123‘)

           以上都是doc指令，功能是导入、建表、插入行等；

 

三、实现步骤一中的功能：

很简单，就把这次的建数据库的代码和上一节建Web表单合并一下：

 

bb.py:

# coding: utf-8

import sys
reload(sys)
sys.setdefaultencoding(‘utf-8‘)

from flask import Flask, render_template,url_for,session,redirect,flash  
from flask_script import Manager  
from flask_bootstrap import Bootstrap  
from flask_moment import Moment  
from flask_wtf import Form  
from wtforms import StringField, SubmitField  
from wtforms.validators import Required 
from flask_sqlalchemy import SQLAlchemy   #这里导入框架

app = Flask(__name__)

app.config[‘SQLALCHEMY_DATABASE_URI‘] = ‘mysql://[email protected]/yxctest‘     #自己的MySQL账户和建立的表
app.config[‘SQLALCHEMY_COMMIT_ON_TEARDOWN‘] = True
#app.config[‘SQLALCHEMY_TRACK_MODIFICATIONS‘] = True
db = SQLAlchemy(app)           #db实例
bootstrap = Bootstrap(app)
app.secret_key = ‘1234567‘

class NameForm(Form):   #Web表中定义的几个片段
    name = StringField(‘What is your name?‘, validators=[Required()])
    email = StringField(‘What is your email‘, validators=[Required()])
    password = StringField(‘What is your password‘, validators=[Required()])
    submit= SubmitField(‘Submit‘)


class User(db.Model):     #定义的数据库的表
    __tablename__ = ‘users‘
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(80), unique=True)
    email = db.Column(db.String(320), unique=True)
    password = db.Column(db.String(32), nullable=False)

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





@app.route(‘/‘, methods=[‘GET‘, ‘POST‘])

def index():

    form = NameForm()
    if form.validate_on_submit:
        user = User.query.filter_by(username = form.name.data).first()#查询语句，精确查询输入的name和数据库表中的name比对
        if user is None:
            user = User(username = form.name.data,email=form.email.data,password=form.password.data)#如果不存在，则插入一行
            db.session.add(user)
            db.session.commit()#这两行是必须的
            session[‘known‘] = False
        else:
            session[‘known‘] = True

        session[‘name‘]=form.name.data
        form.name.data = ‘‘
    return render_template(‘index.html‘,form=form,name=session.get(‘name‘),known = session.get(‘known‘,False))



if __name__ == ‘__main__‘:
    app.run(debug=True)

当然我们的模板渲染也得改一下：

 

index.html:

{% extends "bootstrap/base.html" %}

{% import "bootstrap/wtf.html" as wtf %}
{% block title %}TTTTT{% endblock %}

{% block content %}

<div class="container">
<div class="page-header">
<h1>Hello, {% if name %}{{ name }}{% else %}Stranger{% endif %}!</h1>        
{%if not known%}
<p>Please meet you</p>
{%else%}
<p>Happy see you again</p>
{%endif%}

</div>
</div>
{{ wtf.quick_form(form) }}
{% endblock %}

 

效果：