### Lesson: Initializing a New Virtual Environment in Python #### Specific Objective Learn to create and manage isolated Python environments using the `virtualenv` tool, enabling you to manage dependencies for different projects separately. #### Prerequisites - Python installed on your computer. - Basic knowledge of terminal or command line operations. #### Introduction to Virtual Environments A virtual environment in Python is a self-contained directory tree that includes a Python installation and additional packages. Using a virtual environment allows you to work on multiple projects with different dependencies, without conflicts. #### Steps to Initialize a Virtual Environment 1. **Install virtualenv:** If you haven't installed `virtualenv`, you can do so by running the following command in your terminal: ``` pip install virtualenv ``` 2. **Create a New Directory for Your Project:** Make a new directory for your project and navigate into it: ``` mkdir my_project cd my_project ``` 3. **Initialize the Virtual Environment:** Inside your project directory, run the following command to create a new virtual environment: ``` virtualenv venv ``` Here, `venv` is the name of your virtual environment directory. You can name it anything you prefer. 4. **Activate the Virtual Environment:** - On Windows, activate the virtual environment using: ``` .\venv\Scripts\activate ``` - On macOS and Linux, use: ``` source venv/bin/activate ``` After activation, your terminal will usually show the name of your virtual environment (e.g., `(venv)`) to indicate that it’s active. 5. **Verify the Environment:** Your virtual environment should now be active, and you can verify it by checking the Python version or installed packages. Since this is a new environment, it should only contain the default packages: ``` pip list ``` #### Common Use Patterns - **Project Isolation:** Each Python project can have its own virtual environment with independent sets of packages, avoiding conflicts between project dependencies. - **Development and Testing:** Use virtual environments to test different versions of packages or Python itself, ensuring compatibility and stability. #### Cheat Sheet - `pip install virtualenv`: Installs the virtualenv tool. - `mkdir project_name`: Creates a new directory for your project. - `cd project_name`: Changes the current directory to your project's directory. - `virtualenv env_name`: Creates a new virtual environment in the directory `env_name`. - `source env_name/bin/activate` or `.\env_name\Scripts\activate`: Activates the virtual environment. #### Exercise 1. Install `virtualenv` if it’s not already installed. 2. Create a new directory for a project and navigate into it. 3. Initialize a new virtual environment in this directory. 4. Activate the virtual environment and use `pip list` to view the installed packages. #### Resources - virtualenv Documentation: [virtualenv pypa documentation](https://virtualenv.pypa.io/en/latest/) By completing this lesson, you should now be able to create and manage virtual environments in Python, giving you a robust method for handling project-specific dependencies.