# -*- coding: utf-8 -*-
import abc
import importlib
from typing import Any, Optional
__all__ = ['ObjectLoader', 'DefaultObjectLoader', 'set_object_loader', 'get_object_loader']
[docs]class ObjectLoader(metaclass=abc.ABCMeta):
"""
An abstract object loaders. Concrete implementations can be used to identify an
object and load it with that identifier.
"""
[docs] @abc.abstractmethod
def load_object(self, identifier: str) -> Any:
"""
Given an identifier load an object.
Throws a ValueError if the object cannot be loaded.
:param identifier: The identifier
:return: The loaded object
"""
[docs] @abc.abstractmethod
def identify_object(self, obj: Any) -> str:
"""
Get an identifier for an object.
Throws a ValueError if the object cannot be identified.
:param obj: The object to identify
:return: An identifier for the object
"""
[docs]class DefaultObjectLoader(ObjectLoader):
"""
A default implementation for an object loader. Can load module level
classes, functions and constants.
"""
[docs] def load_object(self, identifier: str) -> Any:
try:
mod_name, name = identifier.split(':')
except ValueError as exc:
raise ValueError(f'identifier `{identifier}` has an invalid format.') from exc
try:
mod = importlib.import_module(mod_name)
except ImportError as exc:
raise ValueError(f'module `{mod_name}` from identifier `{identifier}` could not be loaded.') from exc
else:
try:
return getattr(mod, name)
except AttributeError as exc:
raise ValueError(f'object `{name}` form identifier `{identifier}` could not be loaded.') from exc
[docs] def identify_object(self, obj: Any) -> str:
identifier = f'{obj.__module__}:{obj.__name__}'
# Make sure we can load the object
self.load_object(identifier)
return identifier
OBJECT_LOADER: Optional[ObjectLoader] = None
[docs]def get_object_loader() -> ObjectLoader:
"""
Get the plumpy global class loader
:return: A class loader
:rtype: :class:`ObjectLoader`
"""
global OBJECT_LOADER
if OBJECT_LOADER is None:
OBJECT_LOADER = DefaultObjectLoader()
return OBJECT_LOADER
[docs]def set_object_loader(loader: Optional[ObjectLoader]) -> None:
"""
Set the plumpy global object loader
:param loader: An object loader
:type loader: :class:`ObjectLoader`
:return:
"""
global OBJECT_LOADER
OBJECT_LOADER = loader
