# cython: language_level=3, freethreading_compatible=True
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from types import GenericAlias
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from cpython.dict cimport PyDict_GetItem
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from cpython.object cimport PyObject
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cdef extern from "Python.h":
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# Call a callable Python object callable with exactly
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# 1 positional argument arg and no keyword arguments.
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# Return the result of the call on success, or raise
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# an exception and return NULL on failure.
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PyObject* PyObject_CallOneArg(
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object callable, object arg
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) except NULL
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int PyDict_SetItem(
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object dict, object key, PyObject* value
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) except -1
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void Py_DECREF(PyObject*)
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cdef class under_cached_property:
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"""Use as a class method decorator. It operates almost exactly like
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the Python `@property` decorator, but it puts the result of the
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method it decorates into the instance dict after the first call,
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effectively replacing the function it decorates with an instance
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variable. It is, in Python parlance, a data descriptor.
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"""
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cdef readonly object wrapped
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cdef object name
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def __init__(self, object wrapped):
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self.wrapped = wrapped
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self.name = wrapped.__name__
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@property
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def __doc__(self):
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return self.wrapped.__doc__
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def __get__(self, object inst, owner):
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if inst is None:
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return self
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cdef dict cache = inst._cache
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cdef PyObject* val = PyDict_GetItem(cache, self.name)
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if val == NULL:
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val = PyObject_CallOneArg(self.wrapped, inst)
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PyDict_SetItem(cache, self.name, val)
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Py_DECREF(val)
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return <object>val
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def __set__(self, inst, value):
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raise AttributeError("cached property is read-only")
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__class_getitem__ = classmethod(GenericAlias)
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cdef class cached_property:
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"""Use as a class method decorator. It operates almost exactly like
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the Python `@property` decorator, but it puts the result of the
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method it decorates into the instance dict after the first call,
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effectively replacing the function it decorates with an instance
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variable. It is, in Python parlance, a data descriptor.
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"""
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cdef readonly object func
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cdef object name
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def __init__(self, func):
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self.func = func
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self.name = None
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@property
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def __doc__(self):
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return self.func.__doc__
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def __set_name__(self, owner, object name):
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if self.name is None:
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self.name = name
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elif name != self.name:
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raise TypeError(
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"Cannot assign the same cached_property to two different names "
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f"({self.name!r} and {name!r})."
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)
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def __get__(self, inst, owner):
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if inst is None:
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return self
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if self.name is None:
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raise TypeError(
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"Cannot use cached_property instance"
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" without calling __set_name__ on it.")
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cdef dict cache = inst.__dict__
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cdef PyObject* val = PyDict_GetItem(cache, self.name)
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if val is NULL:
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val = PyObject_CallOneArg(self.func, inst)
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PyDict_SetItem(cache, self.name, val)
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Py_DECREF(val)
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return <object>val
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__class_getitem__ = classmethod(GenericAlias)
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