Python Virtual Environments

A virtual environment (venv) creates an isolated space for your project’s packages.

  Without venv:
  - packages get installed globally
  - projects can break each other due to version conflicts
  
  With venv:
  - each project has its own dependencies
  - your computer stays clean
  
  ## Create and activate a venv (step by step)
  
  Create:
  
  ```bash
  python -m venv .venv
  ```
  
  Activate:
  
  ### Windows (PowerShell)
  ```bash
  .venv\Scripts\Activate.ps1
  ```
  
  ### macOS/Linux
  ```bash
  source .venv/bin/activate
  ```
  
  ## Install packages inside the venv
  
  ```bash
  pip install requests
  ```
  
  ## Save dependencies (so others can set up the project)
  
  ```bash
  pip freeze > requirements.txt
  ```
  
  Install from file:
  
  ```bash
  pip install -r requirements.txt
  ```
  
  ## Best practice: .gitignore
  
  Do not commit your environment folder:
  
  ```
  .venv/
  ```
  
  ## Graph: isolation concept
  
  ```mermaid
  flowchart LR
    A[Project A] --> B[(.venv A)]
    C[Project B] --> D[(.venv B)]
    B --> E[Packages A]
    D --> F[Packages B]
  ```
  
  In the next lesson, you will learn *args and **kwargs, which helps you build flexible, reusable functions in professional code.