Typed melding

🟢 Beginner · Lesson 16

Type hints and melding are friends - annotate what you meld and your editor (and your agent) knows every attribute from there on. melder ships py.typed, so checkers see real types, not Any.

Before you run

Use the Beginner guide 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

python UX_and_AIX_experiences/01_beginner/16_typed_melding.py

py -3.14t UX_and_AIX_experiences/01_beginner/16_typed_melding.py

Download this collection · Source on GitHub

Public surface

meld with annotations, the typed root namespace

Code

"""
TIER: beginner (16)
GOAL: Type hints and melding are friends - annotate what you meld and
      your editor (and your agent) knows every attribute from there on.
      melder ships py.typed, so checkers see real types, not Any.
SURFACE EXERCISED: meld with annotations, the typed root namespace
"""
import melder as md


class WeatherService:
    def today(self) -> str:
        return "sunny, 24C"


def main() -> None:
    book: md.Spellbook = md.Spellbook()
    book.bind(spell=WeatherService, existence="unique")
    conduit: md.Conduit = book.conjure()

    # The string selects the spell; the annotation describes the returned object.
    weather: WeatherService = conduit.meld("WeatherService")
    report: str = weather.today()
    assert report == "sunny, 24C"
    print("typed end to end:", report)
    print("hint: annotate melds - autocomplete does the remembering for you")


if __name__ == "__main__":
    main()

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 · Level guide