boltons should be builtins.

release calver changelog

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

And that’s just a small selection. As of April 28, 2024, boltons is 87 types and 170 functions, spread across 29 modules. See them all in the Index, and see what’s new by checking the CHANGELOG.

Installation and Integration

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 dozens of boltons are just an import away:

from boltons.cacheutils import LRU
lru_cache = LRU()
lru_cache['result'] = 'success'

Due to the nature of utilities, application developers might want to consider other integration options. See the Integration section of the architecture document for more details.

Boltons is tested against Python 3.7-3.12, as well as PyPy3.

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, consider filing an issue!


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.

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.

Section listing

(For a quick reference you can ctrl-F, see the Index.)