SortedContainers is an Apache2 licensed sorted collections library, written in pure-Python, and fast as C-extensions.

Python’s standard library is great until you need a sorted collections type. Many will attest that you can get really far without one, but the moment you really need a sorted list, dict, or set, you’re faced with a dozen different implementations, most using C-extensions without great documentation and benchmarking.

In Python, we can do better. And we can do it in pure-Python!

>>> sl = sortedcontainers.SortedList(range(int(1e7)))
>>> 1234567 in sl
>>> sl[7654321]
>>> sl.add(1234567)
>>> sl.count(1234567)
>>> sl *= 3
>>> len(sl)

Note: The snippet above requires at least a half gigabyte of memory. In 64-bit versions of CPython an integer requires about 24 bytes. SortedList will add about 8 bytes per object stored in the container. That’s pretty hard to beat as it’s the cost of a pointer to each object. It’s also 66% less overhead than a typical binary tree implementation (e.g. red-black tree, avl tree, aa tree, splay tree, treap, etc.) for which every node must also store two pointers to children nodes.

SortedContainers takes all of the work out of Python sorted collections – making your deployment and use of Python easy. There’s no need to install a C compiler or pre-build and distribute custom extensions. Performance is a feature and testing has 100% coverage with unit tests and hours of stress.


Alex Martelli, Wikipedia

Good stuff! ... I like the simple, effective implementation idea of splitting the sorted containers into smaller “fragments” to avoid the O(N) insertion costs.

Jeff Knupp, Review of SortedContainers

That last part, “fast as C-extensions,” was difficult to believe. I would need some sort of performance comparison to be convinced this is true. The author includes this in the docs. It is.

Kevin Samuel, Formations Python

I’m quite amazed, not just by the code quality (it’s incredibly readable and has more comment than code, wow), but the actual amount of work you put at stuff that is not code: documentation, benchmarking, implementation explanations. Even the git log is clean and the unit tests run out of the box on Python 2 and 3.

Mark Summerfield, a short plea for Python Sorted Collections

Python’s “batteries included” standard library seems to have a battery missing. And the argument that “we never had it before” has worn thin. It is time that Python offered a full range of collection classes out of the box, including sorted ones.


  • Pure-Python
  • Fully documented
  • Benchmark comparison (alternatives, runtimes, load-factors)
  • 100% test coverage
  • Hours of stress testing
  • Performance matters (often faster than C implementations)
  • Compatible API (nearly identical to popular blist and rbtree modules)
  • Feature-rich (e.g. get the five largest keys in a sorted dict: d.iloc[-5:])
  • Pragmatic design (e.g. SortedSet is a Python set with a SortedList index)
  • Developed on Python 2.7
  • Tested on CPython 2.7, 3.2, 3.3, 3.4, 3.5, 3.6 and PyPy, PyPy3


Installing SortedContainers is simple with pip:

$ pip install sortedcontainers

You can access documentation in the interpreter with Python’s built-in help function:

>>> from sortedcontainers import SortedList, SortedSet, SortedDict
>>> help(SortedList)

API Documentation

If you are looking for information on a specific function, class or method, this part of the documentation is for you.

Indices and Utilities

Apache2 License

A large number of open source projects you find today are GPL Licensed. A project that is released as GPL cannot be used in any commercial product without the product itself also being offered as open source.

The MIT, BSD, ISC, and Apache2 licenses are great alternatives to the GPL that allow your open-source software to be used freely in proprietary, closed-source software.

SortedContainers is released under terms of the Apache2 License.

SortedContainers License

Copyright 2014-2016 Grant Jenks

Licensed under the Apache License, Version 2.0 (the “License”); you may not use this file except in compliance with the License. You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.