Virtual Environments (venv)

When building Python applications, different projects often require different versions of the same external library. If you install all packages globally, upgrading a library for Project A might break Project B.

To solve this, we use Virtual Environments (venv) to create isolated python workspace folders for each project.

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16.2.1 Why Use an Isolated Environment?

Global Python Installation (pip global)
   ├── Project A (requires requests v2.20)  <── Conflict!
   └── Project B (requires requests v2.30)  <── Conflict!

With Virtual Environments:
   ├── Project A ── [venv A] ── requests v2.20 (Isolated)
   └── Project B ── [venv B] ── requests v2.30 (Isolated)

By isolating environments, you guarantee that your project behaves exactly the same way, regardless of what other software is installed on your computer.

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16.2.2 Setup Guide: Step-by-Step

Step 1: Create the Virtual Environment

Open your terminal inside your project directory and run:

# Creates a folder named "myenv" containing isolated Python and pip binaries
python -m venv myenv

Step 2: Activate the Environment

Before you can use the environment, you must activate it. Run the command matching your operating system:

• Windows (PowerShell):

  .\myenv\Scripts\Activate.ps1

• Windows (Command Prompt):

  .\myenv\Scripts\activate.bat

• macOS / Linux (Terminal):

  source myenv/bin/activate

:::note Visual Check Once activated, you will see (myenv) displayed in parentheses at the beginning of your terminal prompt line. This confirms that all packages you install now will go to your isolated workspace! :::

Step 3: Deactivate the Environment

If you want to leave the isolated environment and return to your global computer environment, run:

deactivate

This restores your terminal back to the standard global Python path.