[PYTHON] I summarized the folder structure of Flask

A person who develops web systems using Django all the time. I recently started studying Flask because I wanted to make a simple app in my spare time. It's not good to pack too many settings in one file, so I've put together a directory structure based on MVC.

flask_app
├ common
│ ├ libs
│ └ models  ---model
│ 　 ├ user.py
│ └ ・ ・ ・
├ config　---Settings folder
│ ├ base_setting.py　---Common settings for each environment
│ ├ local_setting.py　---Settings for local development environment
│ └ production_setting.py ---Production environment settings
├ controllers ---controller
│ ├ index.py
│ └ ・ ・ ・
├ interceptors 
│ ├ auth.py ---Authentication system processing
│ └ error_handler.py　---Error handling
├ static　---Static file location
├ templates　---template
│ ├ common
│ │ └ layout.html
│ └ index.html
├ application.py　---Define what is used by multiple files (Flask instance, DB, environment variables, etc.)
├ manager.py ---Application execution script (application entrance)
├ requirements.py ---Library list
└ www.py ---routing

Execution flow

• In application.py, load the initialization and settings of application and db (Like Django, I want to start the app with a command (`` python manager.py runserver```), so I use Flask_script Manager)
• Read and route the application that bit the Manager at www.py
• Read db with models and define the model
• Run the routed application in manager.py

Description of file role

I will explain in order.

app.config.from_pyfile("config/base_setting.py")First read the common settings with. The settings that change depending on the environment (development / production) are the environment variables ops set in advance._Changed to read different config file depending on different value of config.

#### **`flask_app/application.py`**
```flask

from flask import Flask
from flask_script import Manager
from flask_sqlalchemy import SQLAlchemy
import os
app = Flask(__name__)

manager = Manager(app)
app.config.from_pyfile("config/base_setting.py")

# linux export ops_config=local|production
# windows set ops_config=local|production
if "ops_config" in os.environ:
    app.config.from_pyfile("config/%s_setting.py" % (os.environ['ops_config']))

db = SQLAlchemy(app)

The contents of controllers are divided by function and integrated using blueprint at www.py.

flask_app/www.py

from interceptors.errorHandler import *
from interceptors.Auth import *
from application import app
from controllers.index import index_page

from flask_debugtoolbar import DebugToolbarExtension
toolbar = DebugToolbarExtension(app)


app.register_blueprint(index_page, url_prefix="/")

Define the model in models. Here, a test model is defined in user.py.

flask_app/common/models/user.py

from application import db


class User(db.Model):
    __tablename__ = 'user'

    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    name = db.Column(db.String(20), nullable=False)

Define the actual processing in controllers.

flask_app/controllers/index.py

from flask import Blueprint, render_template
from common.models.user import User

index_page = Blueprint("index_page", __name__)


@index_page.route("/")
def index():
    name = "hello"
    context = {"name": name}
    context["user"] = {"nickname": "xxxx",
                       "id": "xxxxx", "home_page": "http://www.xxx"}
    context["num_list"] = [1, 2, 3, 4, 5]

    result = User.query.all()
    context['result'] = result

    return render_template("index.html", **context)

Register the commands runserver and create_all with the manager's add_commend method.

flask_app/manager.py

 from application import app, db, manager
from flask_script import Server, Command
from www import *

# web server
manager.add_command("runserver", Server(host = "0.0.0.0", use_debugger=True, use_reloader=True))

# create tables
@Command
def create_all():
    from common.models.user import User  
    db.create_all()

manager.add_command("create_all", create_all)

def main():
    manager.run()
    
if __name__ == "__main__":
    # app.run( host = "0.0.0.0" )
    
    try:
        import sys
        sys.exit( main() )
    except Exception as e:
        import traceback
        traceback.print_exc()

Run

• `pip install -r requirements.py` to install the required modules.
• In `flask_app / local_setting.py`, set the user, password, host and port of db according to your environment.
• Create a DB with the name flask in your environment.
• Hit `` `python manager.py create_all``` under the project folder (flask_app). A master with the name user is generated.
• Hit python manager.py runserver and

http://localhost:Access 5000 and succeed when the next screen appears!

 ![flask_app_image.JPG](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/545184/b64db0c9-64cf-0b1b-e7a8-9935f14b5008.jpeg)


## Source
 I uploaded the source to gitHub, so if you have time, please download it (https://github.com/shixujapan/flask_app) and play with it.
## What to do next

 * Create a simple CRUD app using Flask
 * Consider cooperation with Vue.js