picos.caching

Caching helpers.

Outline

Classes

cached_property	A read-only property whose result is cached.
cached_selfinverse_property	A read-only, self-inverse property whose result is cached.

Functions

borrow_cache	Copy cached values from one object to another.
cached_selfinverse_unary_operator	Make a self-inverse unary operator method cache its result.
cached_unary_operator	Make a unary operator method cache its result.
empty_cache	Clear all cached values of an object.
unlocked_cached_properties	Unlock the setters of cached instance attributes.

Data

CACHED_PREFIX

CACHED_PROP_UNLOCKED_TOKEN

Classes

cached_property

class picos.caching.cached_property(fget=None, fset=None, fdel=None, doc=None)

Bases: property

A read-only property whose result is cached.

__init__(fget=None, fset=None, fdel=None, doc=None)

deleter(fdel)

getter(fget)

setter(fset)

cached_selfinverse_property

class picos.caching.cached_selfinverse_property(fget=None, fset=None, fdel=None, doc=None)

Bases: picos.caching.cached_property

A read-only, self-inverse property whose result is cached.

Functions

borrow_cache

picos.caching.borrow_cache(target, source, names)

Copy cached values from one object to another.

Parameters

• target – The object to populate the cache of.

• source – The object to take cached values from.

• names – Names of cached properties or functions to borrow.

cached_selfinverse_unary_operator

picos.caching.cached_selfinverse_unary_operator(operator)

Make a self-inverse unary operator method cache its result.

This is supposed to be used for property-like special methods such as __neg__ where cached_property can’t be used.

Warning

The result returned by the wrapped operator must be a fresh object as it will be modified.

cached_unary_operator

picos.caching.cached_unary_operator(operator)

Make a unary operator method cache its result.

This is supposed to be used for property-like special methods such as __neg__ where cached_property can’t be used.

empty_cache

picos.caching.empty_cache(obj)

Clear all cached values of an object.

unlocked_cached_properties

picos.caching.unlocked_cached_properties(obj)

Unlock the setters of cached instance attributes.

Normally, cached attributes are read-only properties. When the user first reads them, the cache is populated with the value returned to the user, and successive reads will return the cached value.

The user is allowed to empty the cache by using del on the variable, but they may not assign a value to it. This context allows the programmer to manually populate the cache by assigning a value to the property.

Example

>>> from picos.caching import cached_property, unlocked_cached_properties
>>> class A:
...     @cached_property
...     def p(self):
...         return 1
...
>>> a = A()
>>> try:
...     a.p = 2
... except AttributeError:
...     print("Not possible.")
...
Not possible.
>>> with unlocked_cached_properties(a):
...     a.p = 2  # Populate the cache of a.p.
...
>>> a.p
2

Data

picos.caching.CACHED_PREFIX

The prefix used for storing cached values.

picos.caching.CACHED_PROP_UNLOCKED_TOKEN

An attribute name whose presence unlocks the setter of cached properties.