Setting up VS Code for Python

A few VS Code extensions catch mistakes while you type and keep your code neat without any effort from you. Set them up once and they work in every project.

Step 1: Install the extensions

Open the Extensions view (⌘⇧X on macOS, Ctrl Shift X on Windows). Search for each of these and click Install. Check the publisher name, because there are lookalikes:

Step 2: Turn on Ruff when you save

Ruff catches things like:

• imports you never use
• variables you created but forgot to use
• messy spacing and layout
• a handful of common mistakes

To have Ruff fix what it can every time you save, add some settings to VS Code:

1. Open the Command Palette (⌘⇧P on macOS, Ctrl Shift P on Windows).
2. Type user settings json and choose Preferences: Open User Settings (JSON).
3. Add the "[python]" block below, then save the file.

{
  "[python]": {
    "editor.formatOnSave": true,
    "editor.defaultFormatter": "charliermarsh.ruff",
    "editor.codeActionsOnSave": {
      "source.fixAll.ruff": "explicit",
      "source.organizeImports.ruff": "explicit"
    }
  }
}

If the file already has settings in it, don't paste a second pair of outer curly braces { }. Add a comma after the last existing setting, then paste only the "[python]": { ... } part inside the existing braces.

These are your user settings, so they apply to every project you open. Don't put them in a project's settings instead: projects can come with their own settings, which would replace yours.

Step 3: Try it

In your learn-python project, replace the contents of main.py with this messy code and save it:

import os
import json

def main():
    total=4500+12800
    unused = 5
    print( "Total:",total )

main()

When you save, Ruff:

• deletes the two imports you don't use
• fixes the spacing, so total=4500+12800 becomes total = 4500 + 12800
• underlines unused to warn you it's never used, but leaves it for you to decide

Run it with uv run main.py to check it still prints Total: 17300.