Boltons

boltons should be builtins.

Boltons is a set of over 230 BSD-licensed, pure-Python utilities in the same spirit as — and yet conspicuously missing from — the standard library, including:

Atomic file saving, bolted on with fileutils
A highly-optimized OrderedMultiDict, in dictutils
Two types of PriorityQueue, in queueutils
Chunked and windowed iteration, in iterutils
Recursive data structure iteration and merging, with iterutils.remap
Exponential backoff functionality, including jitter, through iterutils.backoff
A full-featured TracebackInfo type, for representing stack traces, in tbutils

Full and extensive docs are available on Read The Docs. See what's new by checking the CHANGELOG.

Boltons is tested against Python 3.7-3.14, as well as PyPy3.

Installation

Boltons can be added to a project in a few ways. There's the obvious one:

pip install boltons

On macOS, it can also be installed via MacPorts:

sudo port install py-boltons

Then, thanks to PyPI, dozens of boltons are just an import away:

from boltons.cacheutils import LRU
my_cache = LRU()

However, due to the nature of utilities, application developers might want to consider other options, including vendorization of individual modules into a project. Boltons is pure-Python and has no dependencies. If the whole project is too big, each module is independent, and can be copied directly into a project. See the Integration section of the docs for more details.

Third-party packages

The majority of boltons strive to be "good enough" for a wide range of basic uses, leaving advanced use cases to Python's myriad specialized 3rd-party libraries. In many cases the respective boltons module will describe 3rd-party alternatives worth investigating when use cases outgrow boltons. If you've found a natural "next-step" library worth mentioning, see the next section!

Gaps

Found something missing in the standard library that should be in boltons? Found something missing in boltons? First, take a moment to read the very brief architecture statement to make sure the functionality would be a good fit. It covers the design philosophy, what belongs in boltons, and how modules are organized.

Then, if you are very motivated, submit a Pull Request. Otherwise, submit a short feature request on the Issues page, and we will figure something out.

Development

Install uv, then set up a dev environment:

uv venv && uv pip install -e .

Run the test suite (includes doctests):

uvx --with tox-uv tox -e py314

Run all environments in parallel:

uvx --with tox-uv tox -p auto

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