xpropcache

Lightweight utilities for cached properties with selective reset and pickle-safe classes.

• Extends functools.cached_property with flags
• Class decorator for automatic registration
• Selective cache invalidation
• Automatic cleaning of cache values and marked attributes for pickling

The xpropcache decorator is @PropCache.cached_property | @PropCache.cached_property(flags)

these properties are referred as xprops below

Installation

• Pure Python, no external dependencies except standard library
• Python 3.10+ required

pip install xpropcache --upgrade

Quickstart

from xpropcache import PropCache, F__PickleIgnore__

FLAGS_DB = 0x01

@PropCache
class User:
    
    uid: int
    
    # ignore during pickling
    _session: Session | F__PickleIgnore__

    def __init__(self, uid, loader, session=None):
        self.uid = uid
        self._loader = loader
        self._session = session

    @PropCache.cached_property
    def profile(self):
        return self._loader.load_profile(self.uid)

    @PropCache.cached_property(FLAGS_DB)
    def settings(self):
        return self._loader.load_settings(self.uid)

u = User(42, loader)
if not u.profile:  # computed and cached
    new_user(u)
    PropCache.cp_purge(u)  # invalidates all xprops
elif u.settings.is_premium:  # computed and cached
    ...
    PropCache.cp_reset_by_flag(u, FLAGS_DB)  # only invalidates settings

Concepts

• @PropCache.cached_property | @PropCache.cached_property(flags):
  • Like functools.cached_property, with additional optional flags (int) for grouping.
  • Cached values are ignored during pickling.
• @PropCache:
  • Decorator for classes. Registers xprops, extends __getstate__, and adds __cp_purge__.
• F__PickleIgnore__:
  • Marker type for type annotations. Attributes annotated with this type (directly or in union) are removed during pickling (in addition to cached xprops).

API (short)

• PropCache.cp_purge(inst): Reset all cached xprops of the instance.
• PropCache.cp_reset_by_flag(inst, flags): Reset cached xprops of the instance whose flag bits apply (xprop.flags & flags).
• PropCache.pickle_purge(inst, inst.__dict__): Removes cached xprops and attributes marked with F_PickleIgnore__ from __dict__
• Classes automatically receive:
  • __getstate__ with the pickle-purge logic
  • __cp_purge__: alias to PropCache.cp_purge(self)

Notes

• Inheritance: xprops and F_PickleIgnore__ flags are merged via the MRO.

Changelog

0.3 - fix

• filters the generic object.__getstate__

0.2

• cache entries are now also accessible via subtypes

...
@PropCache
class User:
    ...

class PremiumUser(User):
    ...

pu = PremiumUser(42, loader)
PropCache.cp_purge(pu)

0.1

Initial release