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from types import GenericAlias |
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cdef _sentinel = object() |
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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, 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, 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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val = cache.get(self.name, _sentinel) |
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if val is _sentinel: |
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val = self.wrapped(inst) |
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cache[self.name] = val |
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return 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, 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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val = cache.get(self.name, _sentinel) |
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if val is _sentinel: |
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val = self.func(inst) |
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cache[self.name] = val |
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return val |
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__class_getitem__ = classmethod(GenericAlias) |
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