pip & Package Management

At the end of Python Essentials you got the map of pip and virtual environments. This module is where the map becomes muscle memory — by the end you'll set up projects exactly the way professionals do.

pip (Pip Installs Packages) downloads packages from PyPI — the Python Package Index, a public library of over 500,000 packages. Need to make HTTP calls? requests. Crunch data? pandas. Build a website? flask. Someone has already written, tested, and shared the hard part:

pip install requests

One command, and import requests works in your code.

The commands you'll actually use, in rough order of frequency:

# Install the latest version of a package
pip install requests

# Install an EXACT version
pip install requests==2.31.0

# Upgrade a package you already have
pip install --upgrade requests

# List everything installed
pip list

# Details about one package (version, location, dependencies)
pip show requests

# Remove a package
pip uninstall requests

No restart needed — the moment pip install finishes, the package is importable.

Why pin versions with ==? Because "latest" changes.

If you install flask today and a teammate installs flask next month, you may get different versions with different behavior — the classic "works on my machine" bug. Pinning makes installs reproducible:

pip install flask==3.0.0        # exact version
pip install "flask>=2.0,<4.0"  # an acceptable range

In real projects, versions get pinned in a file (requirements.txt — two lessons from now) rather than typed by hand.