Python Virtual Environment

What is a Virtual Environment?

A virtual environment in Python is an isolated environment on your computer, where you can run and test your Python projects. It allows you to manage project-specific dependencies without interfering with other projects or the original Python installation.

Think of a virtual environment as a separate container for each Python project. Each container:

Has its own Python interpreter
Has its own set of installed packages
Is isolated from other virtual environments
Can have different versions of the same package

Using virtual environments is important because:

It prevents package version conflicts between projects
Makes projects more portable and reproducible
Keeps your system Python installation clean
Allows testing with different Python versions

Creating a Virtual Environment

Python has the built-in venv module for creating virtual environments. To create a virtual environment on your computer, open the command prompt, and navigate to the folder where you want to create your project, then type this command:

Run this command to create a virtual environment named myfirstproject:

Example

python -m venv myfirstproject

Result

This will set up a virtual environment, and create a folder named "myfirstproject" with subfolders and files, like this:

myfirstproject
  Include
  Lib
  Scripts
  .gitignore
  pyvenv.cfg

Activate Virtual Environment

To use the virtual environment, you have to activate it with this command:

Activate the virtual environment:

Example

myfirstproject\Scripts\activate

Result

After activation, your prompt will change to show that you are now working in the active environment:

(myfirstproject) C:\Users\Your Name>

Install Packages

Once your virtual environment is activated, you can install packages in it, using pip. We will install a package called 'cowsay':

Install 'cowsay' in the virtual environment:

Example

pip install cowsay

Result

'cowsay' is installed only in the virtual environment:

Collecting cowsay
  Downloading cowsay-6.1-py3-none-any.whl.metadata (5.6 kB)
  Downloading cowsay-6.1-py3-none-any.whl (25 kB)
Installing collected packages: cowsay
Successfully installed cowsay-6.1

Using Package

Now that the 'cowsay' module is installed in your virtual environment, let's use it to display a talking cow. Create a file called test.py on your computer. You can place it wherever you want, but I will place it in the same location as the myfirstproject folder - not in the folder, but in the same location. Open the file and insert these three lines in it:

Insert two lines in test.py:

Example

import cowsay

cowsay.cow("Hello World")