Example with the

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Example with the#

the is an entity query wrapper like the an. But, unlike the an which allows for multiple solutions, the only allows one possible solution. If the is used and more than one solution was found, an error will be raised.

This is similar to one in SQL.

Example Usage#

from dataclasses import dataclass

from typing_extensions import List

from entity_query_language import entity, let, the, MultipleSolutionFound, symbol, symbolic_mode


@symbol
@dataclass
class Body:
    name: str

@symbol
@dataclass
class World:
    id_: int
    bodies: List[Body]


world = World(1, [Body("Body1"), Body("Body2")])

with symbolic_mode():
    body1 = the(entity(body := let(type_=Body, domain=world.bodies),
                       body.name.startswith("Body1"))).evaluate()
    try:
        body = the(entity(body := let(type_=Body, domain=world.bodies),
                          body.name.startswith("Body"))).evaluate()
        assert False
    except MultipleSolutionFound:
        pass

body1 will execute successfully giving one solution wich is the body with the name Body1. body will raise an error is there is multiple bodies which have a name that starts with Body.

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