tempcache 0.0.14

Python library to cache data and function results in temporary files

Python library to cache data and function results in temporary files

This library offers a simple way to cache data and function results using temporary files, including a mechanism for automatic expiration after a certain time. This library is best suited for slow or expensive functions that return large or complex results. Each item is saved as a separate file whose name is computed by serializing the inputs and hashing the result into a unique file name.

Basic usage

Caching is done through a TempCache class instance that manages cache items in a dedicated caching folder. The first parameter should be the name to use as temp sub-folder or alternatively the absolute path of the cache folder. The caching folder will be created if it does not already exist.

A TempCache instance can be used as a decorator to wrap a function and automatically cache its results. Optional parameters include max_age (expiry in seconds) and pickler (custom pickler like cloudpickle for non-picklable objects).

from tempcache import TempCache

cache = TempCache("mycache", max_age=86_400) # One day

@cache.wrap
def long_running(...):
    ...

result = long_running(...)

Caching results at the call site

You can also use a TempCache instance to cache a function call directly at the call site with the cache_result method.

from tempcache import TempCache

cache = TempCache("mycache", max_age=86_400) # One day

def long_running(...):
    ...

result = cache.cache_result(long_running, ...)

Manual caching

For fine-grained control you can manage cache entries directly. Any pickle-able value can be used as a key — it gets hashed into a digest string that identifies the cache entry.

cache = TempCache("mycache", max_age=86_400)

digest = cache.key_digest(my_key)

result = cache.try_load(digest)

if result is None:
    result = compute(my_key)
    cache.try_save(digest, result)

Clearing the cache

Expired items are removed automatically on read, but you can also trigger cleanup explicitly.

cache.clear_items()                # remove expired items
cache.clear_items(all_items=True)  # remove everything

Isolating caches with source

If two caches share the same folder, identical keys will collide. Use source to namespace them:

cache_a = TempCache("mycache", source="feed-a")
cache_b = TempCache("mycache", source="feed-b")

The same key will produce different digests in each cache.

Examples

Examples notebooks are in the extras folder.

Installation

You can install this package with pip.

pip install tempcache

Related projects

• joblib Computing with Python functions
• percache Persistently cache results of callables
• disckcache Disk and file backed cache library compatible with Django
• cloudpickle Extended pickling support for Python objects
• cached_path A file utility for accessing both local and remote files through a unified interface
• cachier Persistent function caching with TTL, supports pickle and MongoDB backends
• cachetools In-memory caching with LRU, TTL and other eviction strategies
• klepto Scientific caching library supporting file, memory and database backends