MagicStack/immutables

Health v2 · maintenance only

Flags: no_license

Adoption not part of the score

1204 stars · 59 forks observed · 2026-08-28

What it is AI-extracted, prompt v1, taxonomy v1, 2026-08-30, confidence not recorded

A high-performance immutable mapping type for Python based on a Hash Array Mapped Trie (HAMT). It is the implementation used in CPython's contextvars module and offers O(log N) set/get operations with hashable, pickleable Map objects.

Use cases

• immutable dictionary for python
• hamt mapping implementation
• hashable frozen mapping type
• efficient copy-on-write dict alternative
• immutable data structures for functional python
• thread-safe immutable map

When to choose

• you need immutable, hashable mappings with fast O(log N) updates
• you want efficient structural sharing instead of dict copy-on-write
• you need bulk mutation APIs that produce new derived maps

When to avoid

• you only need plain mutable dicts
• you need immutable lists or sets rather than mappings
• you require strict O(1) updates for very large mappings

Facets

library · maturity stable

serialization concurrency programming-languages developer-tools python cross-platform immutable-collections hamt functional-datastructures persistent-data-structures cpython algorithms

Member repositories

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