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"""Utility class for generating instances from attribute names."""
import sys
import typing
import weakref
T = typing.TypeVar("T") # pylint: disable=invalid-name
ATTRIBUTE_CONSTRUCTORS: typing.MutableMapping = weakref.WeakKeyDictionary()
ATTRIBUTE_CACHE: typing.MutableMapping = weakref.WeakKeyDictionary()
class AttributeConstructor(typing.Generic[T]):
"""An object that converts attribute access to constructor calls."""
__slots__ = ("__weakref__",)
def __init__(self, constructor: typing.Callable[[str], T]):
ATTRIBUTE_CONSTRUCTORS[self] = constructor
ATTRIBUTE_CACHE[self] = {}
def __getattribute__(self, name: str) -> T:
name = sys.intern(name)
return ATTRIBUTE_CACHE[self].setdefault(
name, ATTRIBUTE_CONSTRUCTORS[self](name)
)
mwchase /
python-structured-data
