Simple flask application with CRUD

use virtualenv

why use virtualenv ?

virtualenv is used to resolve multiple Python projects using different versions of python or python libraries. virtualenv can create isolated Python environments as you wish. learn more about it from virtualenv

install virtualenv

sudo pip install virtualenv
mkdir myproject
cd myproject
virtualenv venv (name venv whatever you like)
source venv/bin/activate  (active venv)
deactivate (deactive venv)

refer flask-virtualenv

active venv and install Flask

source venv/bin/activate 
pip install Flask 

install Flask-SQLAlChemy

source venv/bin/activate
pip install Flask-SQLAlchemy

Simple hello world of Flask

hello world web app , refer Flask_Hello_World

touch app.py

input below code:

from flask import Flask
app = Flask(__name__)
@app.route('/')
def index():
    return 'hello world'

if __name__ == '__main__':
    app.run(host='0.0.0.0',debug=True)

run it, you will see it in your browser youip:5000:

python app.py

try something with database using SQLAlchemy

more than sql

while you can use sql to create database and tables like below:

sqlite3 app.db < schema.sql

here i come to use SQLAlchemy, first time use SQLAlchemy, have installed it prevously. The right place for use SQLAlchemy in flask read here

create SQLAlchemy db

from flask.ext.sqlalchemy import SQLAlchemy
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///app.db'
app.config['SQLALCHEMY_COMMIT_ON_TEARDOWN'] = True
db = SQLAlchemy(app)

use pragma table_info(table_name) to check table column info.

create your model

it is easy to create your model

from app import db
class Post(db.Model):
    __tablename__='post'
    id = db.Column(db.Integer, primary_key=True)
    title = db.Column(db.String,nullable=False)
    content=db.Column(db.String,nullable=False)
    def __init__(self,title,content):
        self.title = title
        self.content=content

where to create the table ? will create the models. refer flask-sqlalchemy-api

db.create_all()

use Blueprint

why use Blueprint? refer flask-blueprint

At first , you may write all your routes in the main py file , when it gets more and more, it's better to seperate them to different part. Use Blueprint can help seperate handle different part urls in different module/file.

register blueprint in the main py file.

app.register_blueprint(items_blueprint)

items_blueprint can handle related urls in its own module.

items_blueprint = Blueprint(
        '/',__name__,
        template_folder='templates'
        )

@items_blueprint.route('/')
def home():
    items = Items.query.all()
    return render_template('home.html',items=items)

use wtf

why use wtforms and flask-wtf?

use wtfforms in flask make you handle form easily.

1.Create a form object.

from flask_wtf import Form
from wtforms import StringField
from wtforms.validators import DataRequired

class MyForm(Form):
name = StringField('name', validators=[DataRequired()])

2.render form in template

<form method="POST" action="/">
    {{ form.hidden_tag() }}
    {{ form.name.label }} {{ form.name(size=20) }}
    <input type="submit" value="Go">
</form>

3.handle data in post method.

@app.route('/submit', methods=('GET', 'POST'))
def submit():
    form = MyForm()
    if form.validate_on_submit():
        return redirect('/success')
    return render_template('submit.html', form=form)