How to Create and Use a Virtual Environment in Python with venv

Why use a Virtual Environment?

You've likely encountered the frustration of package conflicts. Imagine working on Project A that requires Django 3.2, while Project B needs Django 4.1. Without proper isolation, installing one version overwrites the other, potentially breaking your applications. This is where Python virtual environments become essential.

The Problem with Global Package Installation

When you install Python packages globally using pip, they all share the same space in your system's Python installation.

This creates several problems: 

• Dependency Conflicts
  Different projects often require different versions of the same package. Installing a newer version for one project can break another project that depends on an older version.
• System Pollution
  Over time, your global Python environment becomes cluttered with packages from various projects, making it difficult to track what's actually needed for each project.
• Deployment Issues
  When you're ready to deploy your application, it's nearly impossible to determine exactly which packages and versions your project requires, leading to "it works on my machine" scenarios.

Benefits of Virtual Environments

Virtual environments solve these problems by creating isolated Python installations for each project.

Here are the key benefits:

• Project Isolation
  Each project gets its own set of dependencies, separate from other projects and the system Python installation.
• Version Control
  You can use different versions of the same package across different projects without conflicts.
• Clean Development
  Your global Python installation stays clean, with only essential system packages installed.
• Reproducible Environments
  Virtual environments make it easy to recreate the exact same development environment on different machines or for different team members.

Here's how to use Python's built-in venv module to create and manage virtual environments.

Creating a Virtual Environment

To create a virtual environment, navigate to your project directory and run:

python -m venv myenv

Activating the Environment

Activate the virtual environment based on your operating system:

Windows:

myenv\Scripts\activate

Linux/macOS:

source myenv/bin/activate

Working with Packages

Install packages using pip while your virtual environment is activated:

pip install package_name

List all installed packages:

pip list

Managing Dependencies with requirements.txt

Generate a requirements.txt file with all installed packages:

pip freeze > requirements.txt

Install packages from requirements.txt:

pip install -r requirements.txt

Deactivating and Removing

Deactivate the virtual environment:

deactivate

To remove a virtual environment, simply delete the environment directory:

rm -rf myenv  # Linux/macOS
rmdir myenv /s /q  # Windows

Related Posts

• Use Multiple Python Versions with pyenv
• Use python-dotenv to Load Environment Variables from a .env file in Python
• Check for NaN values in Python

Resources

• Python documentation: venv — Creation of virtual environments