in Flask, Python

Hi. I have been developing Flask applications as a side project for 5 years. After all these years, I found the right structure I need for me.

First Steps

Firstly, I’m always using virtualenv to isolate my projects. For example, we want to develop a poll app.

mkdir poll_app

cd poll_app

virtualenv .

source bin/activate

Python Libraries I Always Use

I’m developing applications that require a database. So, I always use flask_script and flask_migrate libraries. I don’t like Flask’s CLI tool.

I create a python file called manage.py such as Django’s in the root folder. For example;

from MYAPP.data.models import db
from MYAPP import app
from flask_script import Manager
from flask_migrate import Migrate, MigrateCommand

db.init_app(app)
migrate = Migrate(app, db)
manager = Manager(app)

manager.add_command('db', MigrateCommand)

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

I’m using like that;

python manage.py db init # --> init migrations

python manage.py db migrate # --> migrate models

python manage.py db upgrade # --> apply changes

python manage.py db --help # --> :)

Main app file

I create a file app.py in the root folder when I create a new project and then it changes like that.

from MYAPP import app

# To do: This place will change later
config = {
    "development": "config.Development"
}

if __name__ == "__main__":
    app.config.from_object(config["development"])
    app.run()

Config File

I also create a file called config.py in the root folder.


class BaseConfig(object):
    """ Base config class. This fields will use by production and development server """

    ORIGINS = ["*"] # for api calls
    SECRET_KEY = 'YOUR SECRET KEY'

class Development(BaseConfig):
    """ Development config. We use Debug mode """

    PORT = 5000
    DEBUG = True
    TESTING = False
    ENV = 'dev'

# Currently we only have development config.
# If you have production, you will need to pass it to here.
config = {
    'development': 'config.Development'
}

def configure_app(app):
    """ 
        App configuration will be here. 

        Parameters
        ----------

        app : Flask
            app instance
    """

    app.config.from_object(config['development'])

Folder Structure

I create a folder in the root directory. Let’s say folder name is om_core. I create two folders in the om_core.

Their name api and data. The api folder stores application logic and routes. For example, I created a folder called user.

This folder contains two files called init.py and controllers.py file. Our other api layers will be like that. The controller file should be like that;

from flask import Blueprint, jsonify, request

from MYAPP.data.models import db, User

user = Blueprint('user', __name__)

@user.route('/', methods=['GET'])
def get_users():

    return jsonify({ "message": "Hi user :)"})

@user.route('/<int:id>', methods=['GET'])
def users(id):

    return jsonify({ "id": id })

I always use blueprints.

The data folder stores models. For example, I created a file called models.py

from flask_sqlalchemy import SQLAlchemy
from MYAPP import app

# We didn't pass app instance here.
db = SQLAlchemy()

class User(db.Model):
    """ Model for user management """

    id = db.Column(db.Integer, primary_key=True)
    email = db.Column(db.String(100), unique=True)
    password = db.Column(db.String(100))
    name = db.Column(db.String(100))
    surname = db.Column(db.String(100))
    active = db.Column(db.Boolean(), default=True)
    created_at = db.Column(db.DateTime, default=db.func.now())
    updated_at = db.Column(db.DateTime, default=db.func.now())

    def __init__(self, email, password, name, surname, active, created_at, updated_at):
        self.email = email
        self.password = password
        self.name = name
        self.surname = surname
        self.active = active
        self.created_at = created_at
        self.updated_at = updated_at

Let’s get back to the om_core folder. I create a file called init.py to use API layers as endpoints.

from flask import Flask
from flask_cors import CORS

from config import BaseConfig
from config import configure_app

app = Flask(__name__)

from MYAPP.api.user.controllers import user

""" Corst settings will be here. We maybe use this endpoint later. """
cors = CORS(app, resources={
    r'/api/*': {
        'origins': BaseConfig.ORIGINS
    }
})

configure_app(app)

app.url_map.strict_slashes = False

app.register_blueprint(user, url_prefix='/api/users')

You don’t need to use Flask-CORS if you don’t want to allow request from different origins. I’m using it to allow requests from different origins.

Screenshot for My Project Structure

This is a screenshot for my project structure.

That’s all. If you want to see this project on the GitHub: https://github.com/foss-dev/open-monitoring

Thanks for reading.