What is a virtual environment and why is it needed?

A virtual environment is an isolated Python environment where packages are installed only for a specific project, without affecting the global installation.

Why it's needed:

• Different projects might require different versions of the same library.
• To avoid conflicts between dependencies of different projects.
• To lock exact package versions for reproducibility.

Creation and usage (venv):

# Create a virtual environment
python -m venv venv

# Activation
# macOS/Linux:
source venv/bin/activate
# Windows:
venv\Scripts\activate

# Deactivation
deactivate

Package management (pip):

# Install a package
pip install requests

# Install a specific version
pip install requests==2.31.0

# List installed packages
pip list

# Save dependencies to a file
pip freeze > requirements.txt

# Install dependencies from a file
pip install -r requirements.txt

requirements.txt:

requests==2.31.0
flask==3.0.0
pytest==7.4.3

This file locks all project dependencies, allowing you to recreate the environment on another machine.