Flask framework study guide to create a simple blog system

I wrote an article about setting up a flask development environment before. Today I will continue with a practical small project - a blog system.

The blog system is very simple, with only one page, and it is small and well-organized. The purpose here is not to do projects for the sake of doing projects. The original intention of this article is to convey the following knowledge points through this exercise:

1. Understand the directory structure of the flask project from a global perspective

2. The operating mechanism of the flask project

3. Flask framework implements MVC architecture

4. flask-sqlalchemy operates mysql database

1. New project: blog system

In pycharm, create a new flask project, as shown below:

The completed directory structure is like this: very simple, a static folder, a templates folder, and a py file

The above directory structure is the initial structure of flask. This can only cope with small projects. For large and complex projects, we need to introduce package management and MVC architecture design.

2. Restructure the directory structure and introduce package management

For the above structure, in the top-level blog3 directory,

1. Create a new runserver.py file as a unified entry file for the project

2. Create a new blog folder, move the existing static, templates, blog3.py to the blog folder, and then create controller and model folders respectively. Rename blog3.py to __init__.py,

The directory now looks like this:

This is equivalent to a large engineering structure:

1) The top-level blog2 directory is the project name. A project can include multiple modules, that is, applications. Each application has its own configuration file, initialization file, and MVC architecture.

2) runserver.py: at the same level as the application module, as the project startup file

3) Second level blog2 directory: module name

Controller directory: C in MVC, mainly stores view functions

Model directory: M in MVC, mainly stores entity class files and maps tables in the database

Templates: V in MVC, stores html files

Static: Static files, mainly storing css, js and other files

__init__.py: Module initialization file, Flask The creation of program objects must be completed in the __init__.py file, and then we can safely import and reference each package.

Setting.py: Configuration file, database username and password, etc.

3. Develop code

1. Run the project first:

1) Write the __init__.py file and create the project object. The code is as follows:

# -*- coding: utf-8 -*-
from flask import Flask

#创建项目对象
app = Flask(__name__)

from blog3 import app

@app.route('/')
def hello_world():
  return 'Hello World!'
if __name__ == '__main__':
  app.run(debug=True)

from blog2 import db

class User(db.Model):
  __tablename__ = 'b_user'
  id = db.Column(db.Integer,primary_key=True)
  username = db.Column(db.String(10),unique=True)
  password = db.Column(db.String(16))

  def __init__(self,username,password):
    self.username = username
    self.password = password
  def __repr__(self):
    return '<User %r>' % self.username

from blog2 import db

class Category(db.Model):
  __tablename__ = 'b_category'
  id = db.Column(db.Integer,primary_key=True)
  title = db.Column(db.String(20),unique=True)
  content = db.Column(db.String(100))

  def __init__(self,title,content):
    self.title = title
    self.content = content
  def __repr__(self):
    return '<Category %r>' % self.title

# _*_ coding: utf-8 _*_

#调试模式是否开启
DEBUG = True

SQLALCHEMY_TRACK_MODIFICATIONS = False
#session必须要设置key
SECRET_KEY='A0Zr98j/3yX R~XHH!jmN]LWX/,?RT'

#mysql数据库连接信息,这里改为自己的账号
SQLALCHEMY_DATABASE_URI = "mysql://username:password@ip:port/dbname"

# -*- coding: utf-8 -*-
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
app = Flask(__name__)#import os#print os.environ.keys()#print os.environ.get('FLASKR_SETTINGS')#加载配置文件内容app.config.from_object('blog2.setting')   #模块下的setting文件名，不用加py后缀 app.config.from_envvar('FLASKR_SETTINGS')  #环境变量，指向配置文件setting的路径#创建数据库对象 db = SQLAlchemy(app)

E:\workdir\blog2> set FLASKR_SETTINGS=E:\workdir\blog2\blog2\setting.py

E:\workdir\blog2>python
Python 2.7.10 (default, May 23 2015, 09:44:00) [MSC v.1500 64 bit (AMD64)] on wi
n32
Type "help", "copyright", "credits" or "license" for more information.
>>> from blog2 import db
>>> db.create_all()
>>>
>>>

#只有在app对象之后声明，用于导入model否则无法创建表
from blog2.model import User,Category

 <!doctype html>
 <title>Flaskr</title>
 <link rel=stylesheet type=text/css href="{{ url_for('static', filename='style.css') }}">
 <div class=page>
  <h1>Flaskr</h1>
  <div class=metanav>
  {% if not session.logged_in %}
   <a href="{{ url_for('login') }}">log in</a>
  {% else %}
   <a href="{{ url_for('logout') }}">log out</a>
  {% endif %}
  </div>
  {% for message in get_flashed_messages() %}
   <div class=flash>{{ message }}</div>
  {% endfor %}
  {% block body %}{% endblock %}
 </div>

{% extends "layout.html" %}
{% block body %}
 <h2>Login</h2>
 {% if error %}<p class=error><strong>Error:</strong> {{ error }}{% endif %}
 <form action="{{ url_for('login') }}" method=post>
  <dl>
   <dt>Username:
   <dd><input type=text name=username>
   <dt>Password:
   <dd><input type=password name=password>
   <dd><input type=submit value=Login>
  </dl>
 </form>
{% endblock %}

{% extends "layout.html" %}
{% block body %}
 {% if session.logged_in %}
  <form action="{{ url_for('add_entry') }}" method='POST' class=add-entry>
   <dl>
    <dt>Title:
    <dd><input type=text size=30 name=title>
    <dt>Text:
    <dd><textarea name=text rows=5 cols=40></textarea>
    <dd><input type=submit value=Share>
   </dl>
  </form>
 {% endif %}
 <ul class=entries>
 {% for entry in entries %}
  <li><h2>{{ entry.title }}</h2>{{ entry.content|safe }}
 {% else %}
  <li><em>Unbelievable. No entries here so far</em>
 {% endfor %}
 </ul>
{% endblock %}

body      { font-family: sans-serif; background: #eee; }
a, h1, h2    { color: #377BA8; }
h1, h2     { font-family: 'Georgia', serif; margin: 0; }
h1       { border-bottom: 2px solid #eee; }
h2       { font-size: 1.2em; }

.page      { margin: 2em auto; width: 35em; border: 5px solid #ccc;
         padding: 0.8em; background: white; }
.entries    { list-style: none; margin: 0; padding: 0; }
.entries li   { margin: 0.8em 1.2em; }
.entries li h2 { margin-left: -1em; }
.add-entry   { font-size: 0.9em; border-bottom: 1px solid #ccc; }
.add-entry dl  { font-weight: bold; }
.metanav    { text-align: right; font-size: 0.8em; padding: 0.3em;
         margin-bottom: 1em; background: #fafafa; }
.flash     { background: #CEE5F5; padding: 0.5em;
         border: 1px solid #AACBE2; }
.error     { background: #F0D6D6; padding: 0.5em; }

from blog2.model.User import User
from blog2.model.Category import Category
import os

from blog2 import app,db
from flask import request,render_template,flash,abort,url_for,redirect,session,Flask,g

@app.route('/')
def show_entries():
categorys = Category.query.all()
return render_template('show_entries.html',entries=categorys)

@app.route('/add',methods=['POST'])
def add_entry():
if not session.get('logged_in'):
abort(401)
title = request.form['title']
content = request.form['text']
category = Category(title,content)
db.session.add(category)
db.session.commit()
flash('New entry was successfully posted')
return redirect(url_for('show_entries'))

@app.route('/login',methods=['GET','POST'])
def login():
error = None
if request.method == 'POST':
username = request.form['username']
password = request.form['password']
user = User.query.filter_by(username=request.form['username']).first()
passwd = User.query.filter_by(password=request.form['password']).first()

if user is None:
error = 'Invalid username'
elif passwd is None:
error = 'Invalid password'
else:
session['logged_in'] = True
flash('You were logged in')
return redirect(url_for('show_entries'))
return render_template('login.html', error=error)

@app.route('/logout')
def logout():
session.pop('logged_in', None)
flash('You were logged out')
return redirect(url_for('show_entries'))

#只有在app对象之后声明，用于导入view模块
from blog2.controller import blog_manage