Sentinels

Sentinel values that let the @cache_results decorator tell a cached.

None from a cache miss.

CACHE_MISS_SENTINEL is a unique object, passed as the default of a cache read. Getting it back means the key is not cached.
CACHE_NONE_SENTINEL is the string that is stored in place of a None result, because many cache backends can’t tell a stored None from a missing key.

value = cache.get(key, CACHE_MISS_SENTINEL)
if value is CACHE_MISS_SENTINEL:
    ...  # not cached
elif value == CACHE_NONE_SENTINEL:
    value = None  # a cached None

cache_results.sentinels.CACHE_MISS_SENTINEL = <CacheSentinel: CACHE_MISS>: The default of a cache read, returned only when the key is not cached.

cache_results.sentinels.CACHE_NONE_SENTINEL = 'CacheSentinel("CACHE_NONE")': The value stored in place of a None result.

class cache_results.sentinels.CacheSentinel(name: str)[source]

Bases: object

A unique, named marker object.

Two sentinels are never equal unless they are the same object, so one can be passed as the default of a cache read without colliding with any cached value.

Parameters:: name (str) – The name shown by str() and repr().