Cache.pop()

Remove key and return its value, delivering it to exactly one caller.

Usage

Source

Cache.pop(
    key,
    default=None,
)

Reads and decodes the value first, as get does, then deletes exactly that stored version, so a value it can’t read stays for whoever can. A pop that loses that delete to other writers 8 times falls back to removing the row first and decoding afterwards. Only then can a failed decode cost the value: one from a newer version, or any error from a pickle hook. timeout covers the whole call.

Parameters

key: str

The key.

default: Any = None

Returned when the key is missing or expired, or its value file is missing.

Returns

Any

The removed value, or default. With durable=True, a pop whose delete fails returns

default, never the value, which could otherwise be delivered twice. The row stays.

Raises

UnsafeValueError

The value was stored with pickle and this cache has pickle=False. The row stays.

ForeignValueError

on_decode_error='raise', and another version or host might read the value. The row stays.

CorruptValueError

on_decode_error='raise', and no build could read the value. The row is deleted first.

Timeout

Another process held the write lock for longer than timeout, or timeout ran out after losing a race to another writer. This pop deletes nothing, and whatever the other writer left stays.

Examples

token = cache.pop('reset-token:abc')   # None if it was missing or already used