Python VirtualEnv

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:

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

Activate Virtual Environment

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

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

Install Packages

Once your virtual environment is activated, you can install packages in it, using pip.

We will install a package called 'cowsay':

Using Package

Now that the 'cowsay' module is installed in your virtual environment, lets 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:

Then, try to execute the file while you are in the virtual environment:

As a result a cow will appear in you terminal:

Deactivate Virtual Environment

To deactivate the virtual environment use this command:

As a result, you are now back in the normal command line interface:

If you try to execute the test.py file outside of the virtual environment, you will get an error because 'cowsay' is missing. It was only installed in the virtual environment:

Delete Virtual Environment

Another nice thing about working with a virtual environment is that when you, for some reason want to delete it, there are no other projects depend on it, and only the modules and files in the specified virtual environment are deleted.

To delete a virtual environment, you can simply delete its folder with all its content. Either directly in the file system, or use the command line interface like this: