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Double bind outcome๏ƒ

๐ŸŸข Beginner ยท Lesson 30

Binding the SAME class twice is refused - a spell_id is the SHA256 of the class's code, and one object registers once, under any binding name or lifecycle. When one shape must serve two roles, make two shapes: subclass it (see 24).

Before you run๏ƒ

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๏ƒ

python UX_and_AIX_experiences/01_beginner/30_double_bind_outcome.py

py -3.14t UX_and_AIX_experiences/01_beginner/30_double_bind_outcome.py

Download this collection ยท Source on GitHub

Public surface๏ƒ

the one-object law at bind time

Code๏ƒ

 1"""
 2TIER: beginner (30)
 3GOAL: Binding the SAME class twice is refused - a spell_id is the
 4      SHA256 of the class's code, and one object registers once, under
 5      any binding name or lifecycle. When one shape must serve two
 6      roles, make two shapes: subclass it (see 24).
 7SURFACE EXERCISED: the one-object law at bind time
 8"""
 9import melder as md
10
11
12class Doubled:
13    pass
14
15
16class DoubledAgain(Doubled):
17    pass
18
19
20def main() -> None:
21    book = md.Spellbook()
22    book.bind(spell=Doubled, existence="unique")
23    try:
24        book.bind(spell=Doubled, existence="many")
25        print("second bind unexpectedly accepted")
26    except Exception as err:
27        print("same object refused:", type(err).__name__)
28
29    # the fix: a subclass IS a new class - a new spell_id (and a new name)
30    book.bind(spell=DoubledAgain, existence="many")
31    print("subclass bound cleanly - two shapes, two spells")
32
33
34if __name__ == "__main__":
35    main()

Check the outcome๏ƒ

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.

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