# Defaults just work

**🟢 Beginner · Lesson 20**

Your constructor defaults ARE the configuration - a class with default arguments melds without any extra setup. melder calls YOUR __init__; Python fills the defaults.

## Before you run

Use the [Beginner guide](../../beginner/index.md) for prerequisite concepts. Run from a checkout with Melder installed and Python 3.14 free-threading selected. The collection download includes the level's local helper modules.

## Run the saved script

```bash
python UX_and_AIX_experiences/01_beginner/20_defaults_just_work.py
```

```powershell
py -3.14t UX_and_AIX_experiences/01_beginner/20_defaults_just_work.py
```

{download}`Download this collection <../../downloads/beginner-examples.zip>` · [Source on GitHub](https://github.com/Synaptic724/melder/blob/90d52e0a12cb0743d62568d5a19ce954a54443bc/UX_and_AIX_experiences/01_beginner/20_defaults_just_work.py)

## Public surface

plain constructor defaults through meld

## Code

```{literalinclude} ../../downloads/01_beginner/20_defaults_just_work.py
:language: python
:linenos:
```

## Check the outcome

The script contains its own assertions or demonstrated refusal paths. Run it to evaluate those checks against your installed version. The code above is taken directly from the saved file; no run output is invented here.

[More beginner examples](index.md) · [Level guide](../../beginner/index.md)