Lesson 14: Virtual Environments and Dependency Management

Why Virtual Environments Matter

Different Python projects often require different versions of packages. A virtual environment creates an isolated workspace so dependencies don’t conflict with each other or with system‑wide Python installations.

Creating a Virtual Environment

Use Python’s built‑in venv module:

python -m venv venv

Activating the Environment

Windows:

venv\Scripts\activate

macOS/Linux:

source venv/bin/activate

Deactivating the Environment

deactivate

Installing Packages

Once the environment is active, use pip to install packages:

pip install requests
pip install flask

Viewing Installed Packages

pip list

Freezing Dependencies

Save all installed packages to a file:

pip freeze > requirements.txt

Installing from requirements.txt

Recreate the same environment elsewhere:

pip install -r requirements.txt

Upgrading and Uninstalling Packages

pip install --upgrade requests
pip uninstall flask

Using pipx for Global Tools

pipx installs Python tools globally but isolates them in their own environments:

pip install pipx
pipx install black

Best Practices

• Create a virtual environment for every project.
• Commit requirements.txt to version control.
• Never install project dependencies globally.
• Use pip freeze to keep dependencies reproducible.

Next Steps

Now that you can manage environments and dependencies, you're ready to explore how to work with external libraries in Lesson 15: Working with External Libraries (pip).

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