Loader API

The loader module provides unified file loading for all PAL file types.

Loader

Supported File Types

The loader supports three file types:

Prompt Assemblies (.pal) - Main prompt definitions
Component Libraries (.pal.lib) - Reusable components
Evaluation Suites (.eval.yaml) - Test configurations

Loading Methods

Each file type has both sync and async loading methods:

load_prompt_assembly() / load_prompt_assembly_async()
load_component_library() / load_component_library_async()
load_evaluation_suite() / load_evaluation_suite_async()

Examples

Basic file loading:

from pal import Loader
from pathlib import Path

loader = Loader()

# Load a prompt assembly
assembly = loader.load_prompt_assembly("my_prompt.pal")

# Load a component library
library = loader.load_component_library("components.pal.lib")

# Load evaluation suite
evaluation = loader.load_evaluation_suite("examples/evaluation/classify_intent.eval.yaml")

Async loading with context manager:

import asyncio
async def example():
    async with Loader(timeout=60.0) as loader:
        assembly = await loader.load_prompt_assembly_async("prompt.pal")
        library = await loader.load_component_library_async(
            "https://example.com/libs/personas.pal.lib"
        )

asyncio.run(example())

Loading from URLs:

import asyncio

async def load_from_urls():
    loader = Loader(timeout=30.0)

    # Load from GitHub
    library = await loader.load_component_library_async(
        "https://raw.githubusercontent.com/org/repo/main/libs/tasks.pal.lib"
    )

    # Load from any HTTP source
    assembly = await loader.load_prompt_assembly_async(
        "https://example.com/prompts/analysis.pal"
    )

asyncio.run(load_from_urls())

Error Handling

The loader raises specific exceptions:

PALLoadError - File cannot be loaded
PALValidationError - File format is invalid

Example:

from pal import Loader
from pal.exceptions import PALLoadError, PALValidationError

loader = Loader()

try:
    assembly = loader.load_prompt_assembly("invalid.pal")
except PALLoadError as e:
    print(f"Failed to load file: {e}")
except PALValidationError as e:
    print(f"Invalid format: {e}")
    print(f"Validation errors: {e.context['validation_errors']}")