Virtual Environment and Dependency Managers

Virtual Environment and Dependency Managers#

Learning Environments#

Understand the basics and importance of virtual environments and dependency management in Python
Explain why external libraries are used in Python projects
Create and manage virtual environments to isolate project dependencies
Install and manage dependencies using pip and requirements.txt
Activate and deactivate virtual environments to manage different project settings

This session will guide you through the basics of virtual environments and dependency management in Python.

Understanding the Basics#

Why Use External Libraries?#

Most Python projects require external libraries, known as third-party packages or dependencies, like matplotlib. These libraries provide specific functionalities, and sometimes, specific versions are needed for your project.

Dependency Management#

A dependency manager like pip allows you to specify and manage versions of dependencies required for your projects. It handles the installation and updates of these dependencies.

Virtual Environments#

Using a virtual environment (venv in Python) helps isolate and manage project-specific dependencies. This isolation simplifies development, testing, and collaboration across different projects and environments.

Key Steps and Commands#

Creating a Virtual Environment#

Open your terminal or command prompt.
Navigate to your project directory.
Create a virtual environment with: python3 -m venv myenv (replace myenv with your preferred environment name).

Activating the Virtual Environment#

On MacOS/Linux, activate with: source myenv/bin/activate
On Windows, activate with: source myenv/Scripts/activate
Your command prompt will show the environment name in brackets once activated.
Remember, if reactivating later, navigate to your project directory first.

Installing Dependencies#

Install a library, e.g., matplotlib, by running: python3 -m pip install matplotlib
For a specific version, use: python3 -m pip install matplotlib==3.7.0
To view installed dependencies: python3 -m pip list
To remove a dependency: python3 -m pip uninstall package-name

Managing Dependencies with requirements.txt#

Generate a requirements.txt file: python3 -m pip freeze > requirements.txt
This file can be used by others to replicate your environment using: python3 -m pip install -r requirements.txt
Update and maintain this file regularly, especially after changes to your environment.

Deactivating the Virtual Environment#

Simply run deactivate to exit your virtual environment.
The environment name will disappear from your command prompt.

Adapted Content From: Intermediate Research Software Development, The Carpentries Incubator (CC-BY 4.0)