flask 笔记

创建 flask instance（也就是一个应用）两种方式：1. (module) 在URL\my_app.py中加入

from flask import Flask
app = Flask(__name__)

2.(package) 在URL\app_folder\__init__.py中加入

from flask import Flask
app = Flask('app_folder')

import os        
from datetime import datetime       # python 标准库，datetime.utcnow()
from flask import Flask, render_template, session, redirect, url_for, flash        
from flask_bootstrap import Bootstrap       # flask 扩展
from flask_moment import Moment     # flask 扩展
from flask_wtf import FlaskForm
from wtforms import StringField, SubmitField
from wtforms.validators import DataRequired
from flask_sqlalchemy import SQLAlchemy
from flask_migrate import Migrate
from threading import Thread
from flask_mail import Mail, Message

basedir = os.path.abspath(os.path.dirname(__file__))

app = Flask(__name__)       # 创建应用
app.config['SECRET_KEY'] = 'hard to guess string'
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///' + os.path.join(basedir, 'data.sqlite')
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
app.config['MAIL_SERVER'] = 'smtp.googlemail.com'
app.config['MAIL_PORT'] = 587
app.config['MAIL_USE_TLS'] = True
app.config['MAIL_USERNAME'] = os.environ.get('MAIL_USERNAME')
app.config['MAIL_PASSWORD'] = os.environ.get('MAIL_PASSWORD')
app.config['FLASKY_MAIL_SUBJECT_PREFIX'] = '[Flasky]'
app.config['FLASKY_MAIL_SENDER'] = 'Flasky Admin <flasky@example.com>'
app.config['FLASKY_ADMIN'] = os.environ.get('FLASKY_ADMIN')


bootstrap = Bootstrap(app)      # templates 文件夹中 base.html 扩展了 bootstrap/base.html
moment = Moment(app)        # 设置日期、时间的格式。moment.js 由 base.html导入
db = SQLAlchemy(app)        # 创建数据库
migrate = Migrate(app, db)
mail = Mail(app)

class Role(db.Model):
    __tablename__ = 'roles'        # 表格名称
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(64), unique=True)
    users = db.relationship('User', backref='role', lazy='dynamic')          # 与 User 类关联。backref 给 User 类创建 role 属性，在生成 User 对象时通过 role 与一个 Role 对象关联。
    def __repr__(self):        # 直接输出对象或者通过 print 打印对象时，信息都按__repr__方法中定义的格式进行显示。 类似的 __str__ 只有在 print 打印时才生效。便于调试。
        return '<Role %r>' % self.name


class User(db.Model):
    __tablename__ = 'users'
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(64), unique=True, index=True)
    role_id = db.Column(db.Integer, db.ForeignKey('roles.id'))
    def __repr__(self):
        return '<User %r>' % self.username


class NameForm(FlaskForm):
    name = StringField('What is your name?', validators=[DataRequired()])   # DataRequired()要求提交时表单不为空
    submit = SubmitField('Submit')     # 表单的提交按钮。 在 render  html 时，添加 type='Submit' 属性

def send_async_email(app, msg):
    with app.app_context():
        mail.send(msg)

def send_email(to, subject, template, **kwargs):
    msg = Message(app.config['FLASKY_MAIL_SUBJECT_PREFIX'] + ' ' + subject,
                  sender=app.config['FLASKY_MAIL_SENDER'], recipients=[to])
    msg.body = render_template(template + '.txt', **kwargs)
    msg.html = render_template(template + '.html', **kwargs)
    thr = Thread(target=send_async_email, args=[app, msg])
    thr.start()
    return thr

@app.shell_context_processor
def make_shell_context():        # 运行 flask shell 时自动从 app(hello.py) 导入 db, User, Role
    return dict(db=db, User=User, Role=Role)

@app.errorhandler(404)      
def page_not_found(e):        #  404，500 为 html 错误类型
    return render_template('404.html'), 404     # 返回元组

@app.errorhandler(500)
def internal_server_error(e):
    return render_template('500.html'), 500

'''
@app.route('/')
def index():
    return render_template('index.html', current_time=datetime.utcnow())
'''

@app.route('/user/<name>')
def user(name):
    return render_template('user.html', name=name)       # name=name， 前者代表 user.html 中的 name 变量，后者代表由用户在网址栏中输入的值，即<name>


@app.route('/', methods=['GET', 'POST'])        
def index():      # Post/Redirect/Get pattern，inde()被调用两次
    form = NameForm()        # 生成表单实例
    if form.validate_on_submit():        # 表单被提交且通过所有的 validators （这里只有 DataRequired()一个）时返回 True
        old_name = session.get('name')
        if old_name is not None and old_name != form.name.data:
            flash('Looks like you have changed your name!')        # 当两次提交的内容不同时显示提示框。flash() 里的参数被 模板 base.html 中的 get_flashed_messages() 函数提取。
        session['name'] = form.name.data        # 保存表单提交的 data
        return redirect(url_for('index'))        # url_for('index') 返回 root URL。redirect() 发出对 root URL 的 GET请求，作为对 POST 请求的回应。
    return render_template('index.html', form=form, name=session.get('name'))        # 对 redirect() 的 GET请求的回应。

# 加入数据库
@app.route('/', methods=['GET', 'POST'])
def index():
    form = NameForm()
    if form.validate_on_submit():
        user = User.query.filter_by(username=form.name.data).first()        # 查询表单提交的用户名
        if user is None:        # 如果不在数据库中就把它加入
            user = User(username=form.name.data)
            db.session.add(user)
            db.session.commit()
            session['known'] = False  
            if app.config['FLASKY_ADMIN']:
                send_email(app.config['FLASKY_ADMIN'], 'New User', 'mail/new_user', user=user)        
        else:
            session['known'] = True
        session['name'] = form.name.data
        return redirect(url_for('index'))
    return render_template('index.html', form=form, name=session.get('name'), known=session.get('known', False))