diskcache

Diskcache is an open-source Python library that provides a persistent, on-disk cache for Python objects. It offers a dictionary-like interface that stores key–value pairs in a directory on disk, allowing cached data to survive process restarts and to scale beyond available memory.

The library exposes two main interfaces. Cache is designed for single-threaded or single-process usage; FanoutCache is built for multi-process and multi-threaded environments, enabling safe concurrent access to the same cache directory. Both store serialized Python objects on disk and support common operations such as setting, getting, deleting, and clearing items.

Key features include: persistence on disk, optional time-to-live expiration for items, optional total size limit with automatic eviction, and a simple API that mirrors a Python dict. Values are typically serialized (e.g., by pickle) and associated with a cache key derived from the input. The cache can be primed with data that avoids repeated expensive computations and can be used to memoize function results via a built-in memoization decorator.

Uses cases include caching expensive computations, I/O-bound data retrieval, and sharing cached data across processes in long-running applications. Its design emphasizes reliability and performance, offering thread-safety and, for multi-process setups, safe cross-process access to the same cache store.

History and ecosystem: diskcache is an open-source project in the Python ecosystem, distributed via PyPI and hosted on GitHub. It is widely used as a native, disk-backed alternative to in-memory caches when persistence and large caches are desirable.