DEV Community: Ibrahim abo eita

Learning Node-RED Through 6 Practical Labs

Ibrahim abo eita — Mon, 07 Sep 2026 05:18:32 +0000

A collection of 6 Node-RED lab flows for learning the basics: Hello World with Inject/Debug, custom logic with Function nodes, no-code routing with Switch/Change, context exchange across Node/Flow/Global scopes, and MQTT pub-sub with a live dashboard via @flowfuse/node-red-dashboard.

Lab 1: Hello World

*Nodes Used: [Inject - Debug]
*

FLOW: core message flow between 2 nodes with an inject node to reserve the message and debug node to
print the payload.

Inject Node typically used to inject data, start the flow, testing, or periodic cycles
Debug Node inspects the data flowing through the wires (connections between nodes) and is essential for troubleshooting.

Lab 2 - Function Nodes

*Nodes Used: [Inject - Function - Debug]
*

FLOW: same concept as lab 1 but with an additional Function node to process the data passed from the
previous node into different output.

msg.payload = msg.payload + " - processed by Function node";
msg.timestamp = new Date().toISOString();
return msg;

Function Node: Runs custom JavaScript code on the incoming message.

Lab 3 - Switch

*Nodes Used [Inject - Change - Switch - Debug * 2]
*

FLOW: The key idea is to control the flow with no code as we convert the degrees from
celsius to fahrenheit and routing the output to different slots based on the value.

Change Node: Runs on the main event loop of Node-RED,while Function Node is sandboxed JS Execution. Modifies message properties without writing code. Can set, change, move, or delete properties.
Switch Node: Routes a message to different outputs based on rules.

Lab 4 - Context Exchange

*Nodes Used [Inject * 2 - Change * 2 - Debug]
*

FLOW: Node-RED has three scopes of context:
Scope Visibility Typical use
Node Only the single node that set it Private counters, local state inside one
Function node
Flow All nodes on the same tab/flow Shared data for one workflow
Global Entire Node-RED instance Data needed by multiple flows
Context lets you keep data between messages or across different parts of a flow.

Lab 5 - MQTT

*Nodes Used [Inject * 2 - MQTT IN - MQTT OUT - Change - Debug]
*

FLOW: Decoupled communication.

mqtt out node: Publishes a message to a topic on a broker.
mqtt in node: Subscribes to a topic and injects received messages into the flow.

Lab 6 - MQTT

*Nodes Used [Inject * 2 - MQTT IN - MQTT OUT - Change - Debug]
*

FLOW: Installing the @flowfuse/node-red-dashboard palette adds UI nodes. The
dashboard is served at http://localhost:1880/dashboard.

msg.payload = new Date(msg.payload).toLocaleString();
return msg;

I Built an Interactive Python Slicing Quiz (With a Live Sandbox)

Ibrahim abo eita — Tue, 04 Aug 2026 20:36:13 +0000

Python slicing looks simple until it isn’t.

a[1:-1], a[::-2], out-of-bounds indices, slice assignment… these trip up beginners and intermediate devs alike.

So I built a free browser quiz to practice them properly:

40+ questions across difficulty levels
Multiple-choice + type-the-answer modes
A live sandbox where you can try any sequence + start/stop/step and see the result + index visualization
Points, streaks, hints, high scores, keyboard shortcuts
Fully client-side (HTML/CSS/JS)

Play here: https://ibrahim99035.github.io/python-slicing-quiz/
Source: github.com/ibrahim99035/python-slicing-quiz

Feedback welcome — especially on the harder questions and the sandbox UX.

Odoo Fundamentals

Ibrahim abo eita — Mon, 19 May 2025 06:31:08 +0000

What is Odoo in simple points:

Open-source ERP platform that provides a suit for business applications.
It helps companies to manage their operations.
It runs entirely on webserver and has strong modular architecture.
It uses Python for the backend 🐍, PostgreSQL for the database 🐘, modern JavaScript library (called OWL) for frontend 🦉, and XML (Mainly) & CSV (security) for data.
Fully Customizable.

Odoo Object Relational Mapping:

Odoo has a strong ORM that automatically interact with the database without writing raw SQL.
It performs automatic validation for fields.

Odoo modular system:

In Odoo, each functional area is a separate installable module that can depend on other modules, and we can activate or remove what we want to extend the functionality without modifying core code.

Then, the key idea about Odoo is everything is a module, and we can install or uninstall apps like pieces of Lego.

Every app (module or addon) is a python module that has database models, views, business logic, security rules, web controllers & endpoints, reports & actions,..etc.

This modular system makes Odoo a giant collection of modules that interact together.

Odoo Web Library OWL 🦉:

OWL is a Modern JS framework for Odoo's UI similar to react but simpler, lighter, and made specifically for Odoo.
Shortly it is a light-weight reactive JS framework.
Unlike react, the component is always a class and never a function.
OWL files are pure HTML documents and JS scripts (no JSX).
It uses virtual DOM and reactive state for automatic update.

Odoo pre-requirements:

In simple terms, Python - PostgreSQL - XML - JavaScript - Git - Bach
If you tried Python backend development using Flask, FastAPI, or Django you would not face a problem with Odoo backend.
If you tried React as a modern JS framework, OWL would be much easier.
You need a solid knowledge in git and GitHub for cloning the base, push your work, and deployment.
It would be great to learn about XML, and CSV files.
For tools, you would need an IDE like PyCharm, and you can use Visual Studio Code, you would need to install git bash, and you need to install PostgreSQL.

Odoo Cloning:

The GitHub repository for Odoo is github.com/odoo/odoo.

Cloning Odoo:

git clone https://www.github.com/odoo/odoo --depth 1 --branch 18.0 --single-branch odoo_18

--depth 1: is called shallow cloning that only downloads the latest snapshot of the selected branch without full commit history.
--branch 18.0: cloning the branch named 18.0 and it is the current version of Odoo.
--single-branch: clones only the branch we specified.
odoo_18: the name of local folder we are cloning the branch in.

The next step is to install all packages using the command pip install -r requirements.txt.

Odoo configuration file `odoo.conf`

In the root directory of the repo, create a file and name it odoo.conf to add option.

These options could be database configurations, addon paths, admin passwords, and more.

[options]
addons_path = {absolute_path}\odoo18\addons,
          {absolute_path}\odoo18\odoo\addons,

db_user = your_user
db_password = your_password

admin_passwd = your_admin_pass

After doing these steps you could easily start the server by running the command python odoo-main -c odoo.conf.

You must activate developer mode by going to the path localhost:8069/odoo/settings, then scroll down to Developer Tools section and click on Activate the developer mode.

Database Manager:

Built-in tool used to create, duplicate, back up, restore, delete, and manage Odoo databases directly from web browser.

Accessed via: /web/database/manager/
🆕 Create a new database
📂 List existing databases
🔁 Duplicate database
📦 Backup database
♻️ Restore database
❌ Delete database
🔒 Password protection

Admin/master password is needed to access or manage databases
Set via odoo.conf: admin_passwd = yourpassword

Steps to start your new Odoo app:

create a new directory in {root}/odoo in your local repository.
add the absolute path of the new directory as an addon_path in odoo.conf.
create an init.py file within it as it is modular packages.
inside this directory (optionally named custome_addons) you can create all the new apps, so create a directory for your new app.
we have 2 important files to create inside app's directory __init__.py to address app parts, and __manifest__.py to declare it.
create a models/ directory and create an __init__.py within it to address all the models.
create a controllers/ directory and create an __init__.py within it to address all the controllers.
create a views/ for XML files.
restart the server and update apps list from the web UI or you can run python odoo-bin -c odoo.conf -u {app name}.

We may talk in depth about app development in another article.