In this documentation flask project structure will be generated. Flask is a python based microframework with very good documentation which you can find here. At time of writing Flask version 2.0.2 and Python version 3.10.1 was used.
This repository will contain backend for bellik app, which will not have generated views and any static content. It will expose public API, which will be used by web and mobile apps.
It is a de facto to use virtual environment during development. If you are not familiar with virtual environments, please read Virtual environments section in official Flask documentation.
Note that, if you use fish as your shell, command to activate virtual environment is as below:
. venv/bin/activate.fish
If you user bash, command to activate virtual environment is as below:
source venv/bin/activate
You should not commit your virtual environment directory becuase it contains to much local files which just needed to run your code. All packages installed in virtual environment will be downloaded to this directory.
Python projects should have setup.py which contains meta information about package and it’s dependencies. It is very big topic, maybe in future you will need to tweak your setup.py you can read github.com/kennethreitz/setup.py.
Initial setup.py code is below
from setuptools import setup, find_packages
setup(
name='bellikd',
description='Bellik Backend',
version='0.1',
packages=find_packages(),
include_package_data=True,
zip_safe=False,
install_requires=['Flask'],
)
Since there will be no static content or generated content, there is no need for static and templates folders. For project which contains static files and html templates, there is a need for MANIFEST.in file, contents of which are below
recursive-include bellik/static *
recursive-include bellik/templates *
At the beginning of the project you will have file/directory structure similar to as below.
.
├── bellik
│ ├── static
│ └── templates
├── CONTRIBUTING.md
├── docs
├── tests
├── LICENSE
├── MANIFEST.in
├── README.md
└── setup.py
Let’s add bellik/__init__.py file which will have code below.
import os
from flask import Flask
def create_app():
app = Flask(__name__, instance_relative_config=True)
@app.route('/')
def root():
return 'Hello Flask'
@app.route('/hello')
def hello():
return 'Hello!'
return app
Before running the app, please be sure that your virtual environment is active. Now you have to install the app to your virtual environment in development mode, so run python setup.py develop, this command will download dependencies and install your code as a package to your virtual environment as a development package. It means that if you change your code, all your changes will be available if you re-run the server.
There are final steps, we can use flask command line interface to run our development server. Run below commands if you are using fish as your shell.
set -x FLASK_APP 'bellik:create_app()'
set -x FLASK_ENV development
flask run
and below code if you use bash:
export FLASK_APP='bellik:create_app()'
export FLASK_ENV=development
flask run
You will see output something like below:
* Serving Flask app 'bellik:create_app()' (lazy loading)
* Environment: development
* Debug mode: on
* Running on http://127.0.0.1:5000 (Press CTRL+C to quit)
* Restarting with stat
* Debugger is active!
* Debugger PIN: 669-108-668
If you redirect your browser to address in output you will see Hello Flask, if you add navigate to http://127.0.0.1:5000/hello you will see Hello!.
From now on, you have your hello world app running. It is strongly advised by your self experiment with bellik/__init__.py.
When you are developing complex application, you should use unit testing so changes introduced will not introduce bugs or break functionality.
pytest will be used to write tests. Install pytest package in your virtual environment.
pip install pytest
Please read pytest documentation if you are not familiar with unit testing and more details.
Now let’s write first test, create test_bellik.py file in a tests directory. Final project layout will be as below.
.
├── bellik
│ ├── static
│ ├── templates
│ └── __init__.py
├── CONTRIBUTING.md
├── docs
├── tests
│ └── test_bellik.py
├── LICENSE
├── MANIFEST.in
├── README.md
└── setup.py
The contents of test_bellik.py is as below.
import os
import tempfile
import pytest
from bellik import create_app
@pytest.fixture
def client():
app = create_app()
with app.test_client() as client:
yield client
def test_hello_world(client):
rv = client.get('/hello')
assert b'Hello' in rv.data
Please note initializaiton method which is marked with pytest.fixture decorator, which will create application context for testing. Run pytest which will run tests or you can use pytest -v with more verbose output.
You can use .env or .flaskenv files to store your environment variables, which will be loaded automatically by flask command line interface. Please be sure that you install python-dotenv dependency so flask will able to use dotenv files. Contents of .flaskenv file as below.
FLASK_APP='bellik:create_app()'
FLASK_ENV=development