Cachetools timer with datetime.now

A followup to the issue presented in #6953, I'm running into mypy errors when implementing a cache using the mechanism as defined in the cachetools documentation.

Cachetools documentation for TRLUCache with example that matches the implementation below.

My implementation

def expires_in_ttu(_key, value, now):
    expires_in = value[1]
    return now + timedelta(seconds=expires_in)

cache = TLRUCache(maxsize=10, ttu=expires_in_ttu, timer=datetime.now)

The mypy error:

Argument "timer" to "TLRUCache" has incompatible type "Callable[[Optional[tzinfo]], datetime]"; expected "Callable[[], float]"

Workaround:

We can use time.monotonic instead of datetime.now, but:
- the example in the docs use datetime.now
- datetime.now is arguably more familiar to most developers

Versions

• cachetools: 5.2.0
• types-cachetools: 5.2.1

Inizia confrontando il typing di TLRUCache in types-cachetools con l’esempio documentato di datetime.now e il comportamento descritto nell’issue #6953. Riproduci l’errore di mypy segnalato usando le versioni elencate, quindi verifica che l’uso documentato del timer sia accettato oppure che la documentazione e il typing siano coerenti.