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venv/lib/python3.12/site-packages/propcache/_helpers_py.py

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+"""Various helper functions."""
+
+import sys
+from collections.abc import Mapping
+from functools import cached_property
+from typing import Any, Callable, Generic, Optional, Protocol, TypeVar, Union, overload
+
+__all__ = ("under_cached_property", "cached_property")
+
+
+if sys.version_info >= (3, 11):
+    from typing import Self
+else:
+    Self = Any
+
+_T = TypeVar("_T")
+# We use Mapping to make it possible to use TypedDict, but this isn't
+# technically type safe as we need to assign into the dict.
+_Cache = TypeVar("_Cache", bound=Mapping[str, Any])
+
+
+class _CacheImpl(Protocol[_Cache]):
+    _cache: _Cache
+
+
+class under_cached_property(Generic[_T]):
+    """Use as a class method decorator.
+
+    It operates almost exactly like
+    the Python `@property` decorator, but it puts the result of the
+    method it decorates into the instance dict after the first call,
+    effectively replacing the function it decorates with an instance
+    variable.  It is, in Python parlance, a data descriptor.
+    """
+
+    def __init__(self, wrapped: Callable[[Any], _T]) -> None:
+        self.wrapped = wrapped
+        self.__doc__ = wrapped.__doc__
+        self.name = wrapped.__name__
+
+    @overload
+    def __get__(self, inst: None, owner: Optional[type[object]] = None) -> Self: ...
+
+    @overload
+    def __get__(
+        self, inst: _CacheImpl[Any], owner: Optional[type[object]] = None
+    ) -> _T: ...
+
+    def __get__(
+        self, inst: Optional[_CacheImpl[Any]], owner: Optional[type[object]] = None
+    ) -> Union[_T, Self]:
+        if inst is None:
+            return self
+        try:
+            return inst._cache[self.name]  # type: ignore[no-any-return]
+        except KeyError:
+            val = self.wrapped(inst)
+            inst._cache[self.name] = val
+            return val
+
+    def __set__(self, inst: _CacheImpl[Any], value: _T) -> None:
+        raise AttributeError("cached property is read-only")