1#!/usr/bin/env python3
2#
3#  Copyright (c) 2019, The OpenThread Authors.
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29
30from functools import wraps
31
32
33def cached(f):
34    """
35    Decorator to convert a function to cache its return value when it's called by the first time.
36
37    :param f: The function to decorate.
38    :return: The caching function.
39    """
40    cache_key = '_once_' + f.__name__
41
42    @wraps(f)
43    def once_f(self):
44        try:
45            v = object.__getattribute__(self, cache_key)  # can not use getattr, will trigger __getattr__ wrongly
46        except AttributeError:
47            v = f(self)
48            setattr(self, cache_key, v)
49        return v
50
51    return once_f
52
53
54def cached_property(f):
55    """
56    Decorator for declaring a property that caches its value.
57
58    :param f: The property getter function.
59
60    :return: The caching property.
61    """
62    return property(cached(f))
63