Python Virtual Environment Primer

Python Virtual Environment Primer (Windows, macOS, Linux)

This guide helps you create and activate an isolated Python environment using venv on Windows, macOS, and Linux.

Prerequisites

Python 3.x installed (preferably 3.6+)
venv module is included by default with Python 3.3+

Verify your installation:

python --version     # or python3 --version

1. Create a Virtual Environment

To create a virtual environment (named scicomp_env, though you can choose any name), open a terminal or command prompt in your project directory and run the following command:

💻 Windows

python -m venv scicomp_env

🍎 macOS / 🐧 Linux

python3 -m venv scicomp_env

This creates a subdirectory called scicomp_env/ that contains the isolated Python interpreter and dependencies.

2. Activate the Virtual Environment

💻 Windows (Command Prompt)

scicomp_env\Scripts\activate

💻 Windows (PowerShell)

scicomp_env\Scripts\Activate.ps1

Note: If you get an execution policy error in PowerShell, run:
Set-ExecutionPolicy -Scope Process -ExecutionPolicy Bypass

🍎 macOS / 🐧 Linux

source scicomp_env/bin/activate

When activated, your shell prompt will prefix with (scicomp_env).

3. Use the Environment

Once the environment is active:

Install packages with pip, e.g., HamLorenz:
```
pip install hamlorenz
```
These packages will be isolated to the virtual environment.

4. Deactivate the Environment

When you're done working in the virtual environment, deactivate it:

deactivate

5. Optional Tips

Check installed packages:

pip list

Save your environment:

pip freeze > requirements.txt

Recreate environment from file:

pip install -r requirements.txt

Additional Notes

You can safely delete the scicomp_env/ folder to remove the environment.
IDEs like VS Code automatically detect and use the scicomp_env if placed in your project folder.
For project-based work, it is good practice to include the scicomp_env/ folder in your .gitignore.