Python - Virtual Environment

A virtual environment is an isolated Python environment created for a specific project.

It has its own copy of Python, its own pip, and its own set of installed packages. Packages installed inside one virtual environment do not affect other environments or the system Python.

Consider two projects in which we work. One project needs requests version 2.31.0, and the other needs version 2.20.0.

If both projects share the same system Python, installing one version would break the other project.

A virtual environment solves this problem by giving each project its own isolated set of packages.

Python 3 provides the venv module, which is built into the standard library, to create virtual environments.

To create a virtual environment, open a command prompt in the project folder and run the following command:

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• python -m venv runs the venv module as a script.
• myenv is the name of the folder that will contain the new environment.

After running the command, a folder named myenv is created. It contains the environment's own Python executable, pip, and an empty site-packages directory.

Before installing packages, the virtual environment must be activated. The activation command depends on the operating system.

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After activation, the environment name appears at the beginning of the command prompt, like this:

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Once activated, any pip install command installs the package into the virtual environment, not the system Python.

Collecting requests
  Downloading requests-2.31.0 ...
Successfully installed requests-2.31.0

We can confirm that a package was installed inside the environment by checking the version of pip from within it.

C:\Users\name\myproject\myenv\Scripts\python.exe

When we finish working, we can leave the virtual environment using the deactivate command.

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After deactivation, the environment name disappears from the command prompt, and commands again refer to the system Python.

A virtual environment is just a folder. To remove it, delete the folder after deactivating it.

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System Python	Virtual Environment
Shared by all projects.	Created separately for each project.
Installing a package affects all projects.	Installing a package affects only that environment.
Version conflicts are possible.	Version conflicts are avoided.
No activation needed.	Must be activated before use.

• Each project can have its own package versions.
• Conflicts between projects are avoided.
• Dependencies can be installed without administrative permissions.
• An environment can be recreated easily from a requirements.txt file.
• The system Python installation stays clean.