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# Copyright (c) Facebook, Inc. and its affiliates.
from typing import Any
import pydoc
from fvcore.common.registry import Registry # for backward compatibility.
"""
``Registry`` and `locate` provide ways to map a string (typically found
in config files) to callable objects.
"""
__all__ = ["Registry", "locate"]
def _convert_target_to_string(t: Any) -> str:
"""
Inverse of ``locate()``.
Args:
t: any object with ``__module__`` and ``__qualname__``
"""
module, qualname = t.__module__, t.__qualname__
# Compress the path to this object, e.g. ``module.submodule._impl.class``
# may become ``module.submodule.class``, if the later also resolves to the same
# object. This simplifies the string, and also is less affected by moving the
# class implementation.
module_parts = module.split(".")
for k in range(1, len(module_parts)):
prefix = ".".join(module_parts[:k])
candidate = f"{prefix}.{qualname}"
try:
if locate(candidate) is t:
return candidate
except ImportError:
pass
return f"{module}.{qualname}"
def locate(name: str) -> Any:
"""
Locate and return an object ``x`` using an input string ``{x.__module__}.{x.__qualname__}``,
such as "module.submodule.class_name".
Raise Exception if it cannot be found.
"""
obj = pydoc.locate(name)
# Some cases (e.g. torch.optim.sgd.SGD) not handled correctly
# by pydoc.locate. Try a private function from hydra.
if obj is None:
try:
# from hydra.utils import get_method - will print many errors
from hydra.utils import _locate
except ImportError as e:
raise ImportError(f"Cannot dynamically locate object {name}!") from e
else:
obj = _locate(name) # it raises if fails
return obj
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