Base de Conhecimento

Python powers web frameworks like Django and Flask, automation scripts, and data applications. This guide covers installing Python, pip, and virtual environments — the standard workflow for isolating project dependencies.

Prerequisites

• Ubuntu 22.04/24.04 or Debian 11/12 VPS
• Root or sudo access

Step 1 — Check the Pre-Installed Version

python3 --version

Ubuntu and Debian ship with Python 3 by default, though possibly not the latest release.

Step 2 — Install Python and Essential Tools

sudo apt update
sudo apt install python3 python3-pip python3-venv -y

Step 3 — Verify pip

pip3 --version

Step 4 — Installing a Newer Python Version (If Needed)

For a version not available in the default repositories, use the deadsnakes PPA (Ubuntu only):

sudo add-apt-repository ppa:deadsnakes/ppa -y
sudo apt update
sudo apt install python3.12 python3.12-venv -y

Step 5 — Create a Virtual Environment

python3 -m venv myproject-env

Step 6 — Activate the Virtual Environment

source myproject-env/bin/activate

Your shell prompt will show the environment name, confirming it's active.

Step 7 — Install Packages Inside the Virtual Environment

pip install requests flask

Step 8 — Deactivate When Done

deactivate

Why Virtual Environments Matter

Without one, all packages install system-wide, causing version conflicts between different projects requiring different library versions. Every project should have its own isolated environment.

Managing Dependencies with requirements.txt

Export your project's exact dependencies:

pip freeze > requirements.txt

Install from that file on another machine/server:

pip install -r requirements.txt

Running a Test Script

echo "print('Hello from Python')" > hello.py
python3 hello.py

Common Errors

"externally-managed-environment" error installing with pip — recent Ubuntu/Debian versions block system-wide pip installs by default; use a virtual environment instead (the recommended approach) rather than bypassing this protection.

"python: command not found" — use python3 explicitly; the bare python command isn't guaranteed to exist on Debian-based systems.

Best Practices

• Always use a virtual environment per project
• Keep a requirements.txt file in version control for reproducible installs
• Avoid installing packages system-wide with sudo pip

Related Articles

• How to Deploy a Django/Flask Application with Gunicorn and Nginx
• How to Install Nginx on Ubuntu & Debian
• How to Schedule Tasks with Cron on a Linux VPS