pyzim.cache.BaseCache

class documentation

class BaseCache(object):

Known subclasses: pyzim.cache.HybridCache, pyzim.cache.LastAccessCache, pyzim.cache.NoOpCache, pyzim.cache.TopAccessCache

Constructor: BaseCache(on_leave)

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Base class for caches.

When using any of the subclasses of this cache, please use something akin to the following pattern:

    key = ...  # some unique hashable key identifying the element
    if cache.has(key):  # cache hit
        element = cache.get(key)
    else:
        element = ...  # get element outside of cache
        cache.push(key)  # always push element unto the cache

This class does not actually implement anything and serves as a superclass that describes the methods.

Method	`__init__`	The default constructor.
Method	`clear`	Empty this cache.
Method	`get`	Return the element that has been cached for this key.
Method	`has`	Return True if an element is cached for the specific key.
Method	`push`	Push an element for this key into this cache.
Method	`remove`	If an element is cached for key, remove it from the cache.
Instance Variable	`on_leave`	a callable expecting two arguments (key, value) that will be called when an element leaves the cache

def __init__(self, on_leave=None): ¶

overridden in pyzim.cache.HybridCache, pyzim.cache.LastAccessCache, pyzim.cache.TopAccessCache

The default constructor.

Parameters
on_leave:callable or `None`	a callable expecting two arguments (key, value) that will be called when an element leaves the cache

def clear(self, call_on_leave=True): ¶

overridden in pyzim.cache.HybridCache, pyzim.cache.LastAccessCache, pyzim.cache.NoOpCache, pyzim.cache.TopAccessCache

Empty this cache.

Parameters
call_on_leave:`bool`	if nonzero (default), call `BaseCache.on_leave` for each element cleared

def get(self, key): ¶

overridden in pyzim.cache.HybridCache, pyzim.cache.LastAccessCache, pyzim.cache.NoOpCache, pyzim.cache.TopAccessCache

Return the element that has been cached for this key.

Parameters
key:hashable	key for the element that should be returned

Returns
same as passed to `BaseCache.push`	the element

Raises
`KeyError`	if no element was cached for this key

def has(self, key): ¶

overridden in pyzim.cache.HybridCache, pyzim.cache.LastAccessCache, pyzim.cache.NoOpCache, pyzim.cache.TopAccessCache

Return True if an element is cached for the specific key.

Parameters
key:hashable	key of element that should be checked

Returns
`bool`	True if an element has been cached for this key

def push(self, key, element, allow_replacement=True): ¶

overridden in pyzim.cache.HybridCache, pyzim.cache.LastAccessCache, pyzim.cache.NoOpCache, pyzim.cache.TopAccessCache

Push an element for this key into this cache.

It is up for the cache to decide whether the element will actually be cached or not. If allow_replacement=False is set, no other element should be kicked from the cache.

Re-pushing an already cached element will not update the cached element.

Parameters
key:hashable	key which will be used to identify the element
element:any	element to cache
allow_replacement:`bool`	if this value is false, do not cache if this would kick another element from the cache

Returns
`bool`	True if the element is now cached, False otherwise

def remove(self, key, call_on_leave=True): ¶

overridden in pyzim.cache.HybridCache, pyzim.cache.LastAccessCache, pyzim.cache.NoOpCache, pyzim.cache.TopAccessCache

If an element is cached for key, remove it from the cache.

Parameters
key:hashable	key of element to remove
call_on_leave:`bool`	if nonzero (default), call `BaseCache.on_leave` on the removed element

on_leave: callable or None = ¶

a callable expecting two arguments (key, value) that will be called when an element leaves the cache