Adventures in Machine Learning

Building a Scalable Web App with Flask and RethinkDB: A Step-by-Step Guide

Flask is a micro web framework in Python that is used to develop websites and web applications. It is easy to learn and implement, making it a popular choice for developers.

RethinkDB, on the other hand, is a NoSQL database that is known for its scalability and speed. In this article, we will discuss how to set up Flask and RethinkDB for a basic web application and how to add data to it.

Setting up Flask and RethinkDB

Installing RethinkDB

To get started, we need to install RethinkDB. RethinkDB provides detailed instructions for various operating systems such as macOS, Windows, and Linux.

Once the installation is complete, we can move on to the next step.

Installing Python drivers and testing setup

To interact with RethinkDB, we need to install the Python driver for RethinkDB. We can use the pip package manager to install the RethinkDB driver.

pip install rethinkdb

Once we have the RethinkDB driver installed, we can test our setup by creating a connection to the database. We can do this in Python using the following code:

import rethinkdb as r

conn = r.connect(host=’localhost’, port=28015)


If there are no errors, we have successfully set up a connection to RethinkDB.

Setting up a Basic Flask project

Now that we have RethinkDB set up and tested, we need to set up a Flask application that can interact with RethinkDB. First, we need to create a new directory for our project and navigate to it using the terminal.

Then, we can create a new virtual environment and install Flask using pip.

mkdir flask_rethinkdb

cd flask_rethinkdb

python3 -m venv venv

source venv/bin/activate

pip install Flask

After installing Flask, let’s create a new file called and add some basic Flask code:

from flask import Flask

app = Flask(__name__)


def hello_world():

return ‘Hello, World!’

if __name__ == ‘__main__’:

We can test that this basic Flask app is working as expected by running:


We should be able to open our web browser and go to http://localhost:5000/ to see “Hello, World!”.

RethinkDB Config

Now that we have a basic Flask app set up, we need to connect it to RethinkDB. We will create a new file called and add the following code to it:

import rethinkdb as r

r.connect( “localhost”, 28015).repl()

We can then add the following to to test that we have successfully connected to RethinkDB:

from flask import Flask, jsonify

from rethinkdb import RethinkDB

r = RethinkDB()

from config import r

@app.route(‘/api/v1/todos’, methods=[‘GET’])

def get_todos():

cursor = r.db(‘todos’).table(‘todos’).run()

todos = [i for i in cursor]

return jsonify(todos)

Let’s create a new database called ‘todos’ and a new table called ‘todos’ in RethinkDB. We can do this using the RethinkDB console by running the following commands:



Adding data to the app

Adding data manually

Now that we have our Flask app and RethinkDB set up, let’s add some data to our ‘todos’ table. We can do this manually by opening the RethinkDB console and running the following command:

r.db(‘todos’).table(‘todos’).insert({‘title’: ‘Complete Article’, ‘completed’: False}).run()

Displaying Todos

Finally, let’s display the todos in our Flask app. We’ve already added a route to our app that displays all the todos at http://localhost:5000/api/v1/todos.

We can open our web browser and go to that URL to see that our todo has been added to the database and is now being displayed in our web app.


In this article, we learned how to set up Flask and RethinkDB for a basic web application and how to add data to it. We discussed how to install RethinkDB, Python drivers, and how to test our setup.

We also discussed how to set up a basic Flask app, how to connect Flask to RethinkDB, and how to add data to our database manually. Finally, we learned how to display data in our web app.

Flask and RethinkDB are powerful tools that enable us to develop scalable and fast web applications. In the previous sections, we learned how to set up Flask and RethinkDB for a basic web application and how to add data to it.

We also discussed how to display data in our web app. However, you might be wondering what other functionalities we can add to make our app more useful and user-friendly.

Here are some further development ideas:

User Login

Implementing a user login system can help secure the app and provide personalized experiences for users. Flask provides several extensions, such as Flask-Login and Flask-Security, that can help us create a secure login system quickly.

Due Dates

Adding due dates to our to-do items can help us prioritize and manage our tasks better. We can achieve this by adding a due date property to our to-do items in the RethinkDB database and then displaying it in the web app.


Dividing larger tasks into smaller subtasks can help us manage and tackle our tasks more efficiently. We can add a new subtask table to our RethinkDB database, and then allow users to create and manage subtasks for each to-do item.

Now that we have added more functionalities to our app, our code might become more complex and harder to maintain. This is where the need for refactoring and modularizing comes in.

Refactoring and modularizing

Refactoring involves restructuring our codebase to make it more efficient, readable, and maintainable. When we have a large codebase, it can become challenging to maintain if it is not well-organized.

We can use the following techniques to refactor our code:

– Separating our code into smaller, reusable functions. We can group related functions into modules and organize them in a package structure.

– Removing code duplication by consolidating functions and avoiding redundancy. – Breaking our code into logically separated files and directories.

To modularize our app, we can use Flask’s blueprints. Blueprints allow us to group our routes, templates, and static files to make our codebase more organized and maintainable.

We can define a blueprint for each feature of our app and then register them to our Flask app.

API reference

As our app grows, we might need to document our API’s endpoints and functions better. Documenting our API would help other developers who want to use our app understand how to interact with it.

We can use the Swagger UI package to generate an

API reference for our Flask app. This package generates an interactive documentation of our API based on our codebase.

Code Repository and Project Sharing

Finally, it is a good practice to keep your codebase in a version control system to manage changes and track issues. We can use tools such as Git to keep our codebase on a Git hosting platform such as GitHub, GitLab, or Bitbucket.

By hosting our codebase in a Git repository, we can easily collaborate with other developers, track issues, and deploy our app to hosting services such as Heroku. In conclusion, we have discussed how to add more functionalities to our basic Flask and RethinkDB app.

By implementing user login, due dates, and subtasks, we can make our app more useful and user-friendly. To maintain our codebase, we also discussed the need for refactoring and modularizing and documented our API using Swagger UI.

Finally, we emphasized the importance of keeping our codebase in a version control system and collaborating with other developers. With these additional features, we can create a more robust and scalable web app.

This article explored how to set up Flask and RethinkDB for a basic web application, add data to it, and improve its functionalities with user login, due dates, and subtasks. We also discussed the importance of refactoring and modularizing our code to make it more efficient, readable, and maintainable.

Additionally, we explored how documenting our API using Swagger UI, keeping our codebase in a version control system, and collaborating with other developers can help us create a more scalable and robust web app. By following these practices, developers can create powerful web apps that meet user needs and grow over time.

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