EvalFn

API reference for EvalFn

EvalFn

Evaluator that wraps a user-provided function for dynamic evaluation.

This class allows users to create evaluators from any callable function, automatically handling parameter passing, validation, and result conversion to Score objects.

Key Features:

• Dynamic Function Wrapping: Converts any callable into an evaluator

• Argument Validation: Validates that provided arguments match function signature

• Smart Result Conversion: Automatically converts various return types to Score

• Error Handling: Gracefully handles function execution and argument errors

• Parameter Flexibility: Supports functions with any parameter signature

Parameters

Parameter	Type	Required	Default	Description
fn	Callable	✗	None	The callable function to wrap as an evaluator.
score_name	str | None	✗	None	Optional custom name for the score. If not provided, uses the function name.

Example

def equals(a, b):
        return a == b

    evaluator = EvalFn(equals, score_name="exact_match")
    score = evaluator.score(a="hello", b="hello")
    print(score.value)  # 1.0

    def length_check(text, min_length=5):
            return len(text) >= min_length

        evaluator = EvalFn(length_check)

        # Invalid arguments raise TypeError
        try:
                evaluator.score(wrong_param="value")
            except TypeError as e:
                    print(f"Error: {e}")

property name : str

score()

Execute the wrapped function and convert result to Score.

Calls the wrapped function with the provided arguments and converts the result to a Score object. Validates that the provided arguments match the function’s signature.

Parameters

Parameter	Type	Required	Default	Description
*args	Any	✗	None	Positional arguments to pass to the wrapped function.

Returns

A Score object representing the function’s evaluation result. Return type: Score

Raises

TypeError – If the provided arguments don’t match the function signature.

The function result is converted to a Score as follows:

• bool: 1.0 for True, 0.0 for False

• int/float: Direct value conversion

• Score: Returns as-is