immutables ========== .. image:: https://travis-ci.org/MagicStack/immutables.svg?branch=master :target: https://travis-ci.org/MagicStack/immutables .. image:: https://ci.appveyor.com/api/projects/status/tgbc6tq56u63qqhf?svg=true :target: https://ci.appveyor.com/project/MagicStack/immutables An immutable mapping type for Python. The underlying datastructure is a Hash Array Mapped Trie (HAMT) used in Clojure, Scala, Haskell, and other functional languages. This implementation is used in CPython 3.7 in the ``contextvars`` module (see PEP 550 and PEP 567 for more details). Immutable mappings based on HAMT have O(log N) performance for both ``set()`` and ``get()`` operations, which is essentially O(1) for relatively small mappings. Below is a visualization of a simple get/set benchmark comparing HAMT to an immutable mapping implemented with a Python dict copy-on-write approach (the benchmark code is available `here `_): .. image:: bench.png Installation ------------ ``immutables`` requires Python 3.5+ and is available on PyPI:: $ pip install immutables immutables.Map -------------- The ``Map`` object implements ``collections.abc.Mapping`` ABC so working with it is very similar to working with Python dicts. The only exception are its ``Map.set()`` and ``Map.delete()`` methods which return a new instance of ``Map``: .. code-block:: python m1 = Map() # an empty Map m2 = m1.set('key1', 'val1') # m2 has a 'key1' key, m1 is still empty m3 = m2.set('key2', 'val2') m3 = m3.delete('key1') # m3 has only a 'key2' key Further development ------------------- * An immutable version of Python ``set`` type with efficient ``add()`` and ``discard()`` operations. * Add support for efficient ``Map.update()`` operation, allow to pass a set of key/values to ``Map()``, and add support for pickling. License ------- Apache 2.0