CachePlain

ClassSource

cache = CachePlain[Info, Data](cache_size: int)

The plain implementation of the cache, where Info and Data are generic types.

In this project, Info and Data are configured as CachedFileInfo and CachedData, respectively.

This CachePlain instance can only share the cached data among threads. It can be used in normal callbacks. However, in background callbacks, any modifications onCachePlain will be aborted when the callback gets finalized.

Manipulation of this cache is threading-safe.

Aliases

This class can be acquired by

import dash_file_cache as dfc


dfc.CachePlain
dfc.caches.CachePlain
dfc.caches.memory.CachePlain

Arguments

Argument	Type	Required	Description
cache_size	int		The size of the cache, i.e. the maximum of items in the cache. When the cache is full, adding more data in the cache will cause the eldest data to quit from the cache.

Methods

is_in

flag: bool = cache.is_in(key: str)

Check whether key is registered in the cache.

The __contains__ operator is delegated to this method.

Requires

Argument	Type	Required	Description
key	str		The keyword to be validated.

Returns

Argument	Type	Description
flag	bool	If True, the given key value exists in the cache.

---

remove

info: Info = cache.remove(key: str)

Remove the info of one cached item from this cache.

Using this method implies that the data in the cache reaches its end of life. Only the cache item information will still be usable.

Requires

Argument	Type	Required	Description
key	str		The keyword of the data to be removed.

Returns

Argument	Type	Description
info	Info	The light-weighted metadata queried in the cache.

---

dump

cache.dump(key: str, info: Info, data: Data)

Dump data to the cache.

Requires

Argument	Type	Required	Description
key	str		The key value of this new data. If the key exists in the cache, will replace the original value.
info	Info		The light-weighted metadata to be dumped into the cache.
data	Data		The data to be dumped into the cache.

---

load

info, data_loader = cache.load(key: str)

Load the data by a specific keyword.

Requires

Argument	Type	Required	Description
key	str		The key value of to be queried. If key does not exist in the cache, will raise a FileNotFoundError.

Returns

Argument	Type	Description
info	Info	The light-weighted metadata queried in the cache.
data_loader	Callable[[], Data]	The lazy loader for the data. This function implements a deferred loading mechanism allowing that the large-size data to be actually loaded when this method is called.

---

load_info

info: Info = cache.load_info(key: str)

Load the metadata by a specific keyword.

This method is implemented by fetching the returned value load(key)[0].

Requires

Argument	Type	Required	Description
key	str		The key value of to be queried. If key does not exist in the cache, will raise a FileNotFoundError.

Returns

Argument	Type	Description
info	Info	The light-weighted metadata queried in the cache.

---

load_data

data: Data = cache.load_data(key: str)

Load the data by a specific keyword.

This method is implemented by fetching and calling load(key)[1]().

Requires

Argument	Type	Required	Description
key	str		The key value of to be queried. If key does not exist in the cache, will raise a FileNotFoundError.

Returns

Argument	Type	Description
data	Data	The data object queried in the cache. Since data may be large, this value should be a file-like object in most cases.

Properties

cache

cache_dict: LRUDict[str, Tuple[Info, Data]] = cache.cache

Get the low-level LRU cache object of this instance. This value is an LRUDict.

Operators

__contains__

flag: bool = key in cache

Check whether key is registered in the cache.

Requires

Argument	Type	Required	Description
key	str		The keyword to be validated.

Returns

Argument	Type	Description
flag	bool	If True, the given key value exists in the cache.

Examples

See

Cache types