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PythonAdapter

What it is​

  • An in-memory, thread-safe key/value adapter implementing IKeyValueAdapter.
  • Stores values as bytes and supports optional TTL-based expiration using time.monotonic().

Public API​

Class: PythonAdapter(IKeyValueAdapter)​

  • __init__() -> None

    • Initializes an empty in-memory store and a lock.

  • get(key: str) -> bytes

    • Returns the stored value.
    • Raises KVNotFoundError if the key is missing or expired.

  • set(key: str, value: bytes | str | memoryview, ttl: int | None = None) -> None

    • Stores value (normalized to bytes) under key.
    • ttl (seconds) sets an expiration time; None means no expiration.

  • set_if_not_exists(key: str, value: bytes | str | memoryview, ttl: int | None = None) -> bool

    • Stores only if the key does not exist (or has expired).
    • Returns True if inserted, False if the key already exists.

  • delete(key: str) -> None

    • Deletes the key.
    • Raises KVNotFoundError if the key is missing or expired.

  • delete_if_value_matches(key: str, value: bytes | str | memoryview) -> bool

    • Deletes the key only if it exists and its stored value equals the provided value (after normalization).
    • Returns True if deleted, otherwise False.

  • exists(key: str) -> bool

    • Returns True if the key exists and is not expired; otherwise False.

Configuration/Dependencies​

  • Depends on:
    • naas_abi_core.services.keyvalue.KeyValuePorts.IKeyValueAdapter
    • naas_abi_core.services.keyvalue.KeyValuePorts.KVNotFoundError
  • Uses standard library:
    • threading.Lock for synchronization
    • time.monotonic() for TTL expiration

Usage​

import time
from naas_abi_core.services.keyvalue.adapters.secondary.PythonAdapter import PythonAdapter
from naas_abi_core.services.keyvalue.KeyValuePorts import KVNotFoundError

kv = PythonAdapter()

kv.set("a", "hello", ttl=1)
print(kv.get("a"))  # b'hello'

time.sleep(1.1)
print(kv.exists("a"))  # False

try:
    kv.get("a")
except KVNotFoundError:
    print("expired")

Caveats​

  • Storage is in-memory only; data is lost when the process stops.
  • Expired keys are purged lazily (on access via get, set_if_not_exists, delete, delete_if_value_matches, exists), not by a background cleanup thread.
  • TTL is interpreted as seconds and is based on time.monotonic() (not wall-clock time).