property-caching's Introduction

Property caching

Cached version of property

Written and used by the folks at Yola to support our free website builder.

Overview

cached_property - stores results of decorated methods in decorated object (in _cached_properties attribute)
class_cached_property - stores results of decorated methods in the class of decorated object (in _class_cached_properties attribute). All instances will share cached value.
clear_property_cache - deletes cached value (works for object cached properties only)
set_property_cache - explicitly sets property cache (works for object cached properties only)
is_property_cached - allows to check whether property was cached or not (works for object cached properties only)

Usage

from property_caching import (cached_property,
                              class_cached_property,
                              clear_property_cache,
                              set_property_cache,
                              truthy_cached_property)

class Dummy:
    @cached_property
    def foo(self):
        return self.service.expensive_operation()

    @truthy_cached_property
    def bar(self):
        # this value will only be cached if it doesn't evaluate to false:
        return self.service.expensive_operation2()

    @class_cached_property
    def service(self):
        return expensive_service_initialization()

d = Dummy()
d.foo   # calculates result and stores it in d._cached_properties
d.foo   # uses cached value

clear_property_cache(d, 'foo')   # clears cache for property `foo`
set_property_cache(d, 'foo', 42) # explicitly set cache for property `foo`

d2 = Dummy()
d2.foo  # re-calculates value of `foo` but uses cached service