Initial Version

Create your project folder named lr_rest_books_py.

Create a Virtual Environment

It's a good practice to use a virtual environment to isolate your project dependencies. You can create a virtual environment using venv module (built-in to Python 3).

python3 -m venv lrFlaskEnv

Caution:
If you're using git or any other version control system, remember to ignore the virtual environment folder.
e.g. in .gitignore:

+
+lrFlaskEnv/

Activate Virtual Environment

Activate the virtual environment. This step is platform-specific.

On Windows:

lrFlaskEnv\Scripts\activate

On macOS and Linux:

source lrFlaskEnv/bin/activate

Manage dependencies

Create a file named requirements.txt in the root directory of your project. This file will list all the dependencies of your Flask project along with their versions. You can generate this file automatically by using the pip freeze command:

pip3 freeze > requirements.txt

If your virtual environment is set up properly, you should get a empty file named requirements.txt.

Installation

Install Flask framework:

pip3 install Flask

After installation, update requirements.txt:

pip3 freeze > requirements.txt

This command updates the requirements.txt. It should be something similar to this:

blinker==1.7.0
click==8.1.7
Flask==3.0.2
importlib-metadata==7.0.1
itsdangerous==2.1.2
Jinja2==3.1.3
MarkupSafe==2.1.5
Werkzeug==3.0.1
zipp==3.17.0

Create main.py:

from flask import Flask, jsonify

app = Flask(__name__)

@app.route('/ping')
def ping():
    return jsonify({"message": "pong"})

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

Run the program like this:

python3 main.py

You will get result lines like below:

* Serving Flask app 'main'
 * Debug mode: on
WARNING: This is a development server. Do not use it in a production deployment. Use a production WSGI server instead.
 * Running on http://127.0.0.1:5000
Press CTRL+C to quit
 * Restarting with stat
 * Debugger is active!
 * Debugger PIN: nnn-nnn-nnn

Your API server is runnong on port 5000 now.

Note:
You may also choose to use the flask command.

flask --app main run # debug mode off
flask --app hello run --debug # debug mode on

And you don’t need the __main__ part if you’re using the flask command.

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

Try to hit the endpoint /ping with curl command:

curl http://localhost:5000/ping

It shows:

{
  "message": "pong"
}

Nice! Your server is doing well.