Cython implementation of the toolz package, which provides high performance utility functions for iterables, functions, and dictionaries.

toolz is a pure Python package that borrows heavily from contemporary functional languanges. It is designed to interoperate seamlessly with other libraries including itertools, functools, and third party libraries. High performance functional data analysis is possible with builtin types like list and dict, and user-defined data structures; and low memory usage is achieved by using the iterator protocol and returning iterators whenever possible.

cytoolz implements the same API as toolz. The main differences are that cytoolz is faster (typically 2-5x faster with a few spectacular exceptions) and cytoolz offers a C API that is accessible to other projects developed in Cython. Since toolz is able to process very large (potentially infinite) data sets, the performance increase gained by using cytoolz can be significant.

See the PyToolz documentation at and the full API Documentation for more details.


New BSD. See License File.


cytoolz is on the Python Package Index (PyPI):

pip install cytoolz


cytoolz supports Python 3.5+ with a common codebase. It is developed in Cython, but requires no dependecies other than CPython and a C compiler. Like toolz, it is a light weight dependency.

Contributions Welcome

toolz (and cytoolz) aims to be a repository for utility functions, particularly those that come from the functional programming and list processing traditions. We welcome contributions that fall within this scope and encourage users to scrape their files for functions that are broadly useful.

Please take a look at our issue pages for toolz and cytoolz for contribution ideas.