Skip to main content
This is a pre-production deployment of Warehouse. Changes made here affect the production instance of PyPI (
Help us improve Python packaging - Donate today!

An Ordered Set implementation in Cython.

Project Description

An Ordered Set implementation in Cython. Based on Raymond Hettinger’s OrderedSet recipe.


>>> from orderedset import OrderedSet
>>> oset = OrderedSet([1, 2, 3])
>>> oset
OrderedSet([1, 2, 3])
>>> oset | [5, 4, 3, 2, 1]
OrderedSet([1, 2, 3, 5, 4])


  • Works like a regular set, but remembers insertion order;
  • Is approximately 5 times faster than the pure Python implementation overall (and 5 times slower than set);
  • Compatible with Python 2.6 through 3.4.;
  • Supports the full set interface;
  • Supports some list methods, like index and __getitem__.
  • Supports set methods against iterables.


2.0 - 2016-02-02

  • breaking change: All comparisons, other than eq, against other ordered sets are now performed unordered; i.e., they are treated as regular sets.
  • isorderedsubset and isorderedsuperset have been added to perform ordered comparisons against other sequences. Using these methods with unordered collections wield yield arbitrary (and depending on Python implementation, unstable) results.

1.2 - 2015-09-29

  • bugfix: Set operations only worked with iterables if the OrderedSet was on the left-hand side. They now work both ways.
  • bugfix: The order of an intersection was the right-hand side’s order. It is now fixed to be the left-hand side’s order.

1.1.2 - 2014-10-02

  • Make comparisons work with sets and lists, and not crash when compared with None.

1.1.1 - 2014-08-24

  • Add pickle/copy support to OrderedSet

1.1 - 2014-06-04

  • Make OrderedSets handle slicing in __getitem__().

1.0.2 - 2014-05-14

  • Add proper attribution and licenses.

1.0.1 - 2014-05-13

  • Don’t require Cython to build an sdist.

1.0 - 2014-05-11

  • First implementation.

Release History

This version
History Node


History Node


History Node


History Node


History Node


History Node


History Node


History Node


Download Files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

File Name & Hash SHA256 Hash Help Version File Type Upload Date
(78.0 kB) Copy SHA256 Hash SHA256
Source Feb 2, 2016

Supported By

WebFaction WebFaction Technical Writing Elastic Elastic Search Pingdom Pingdom Monitoring Dyn Dyn DNS Sentry Sentry Error Logging CloudAMQP CloudAMQP RabbitMQ Heroku Heroku PaaS Kabu Creative Kabu Creative UX & Design Fastly Fastly CDN DigiCert DigiCert EV Certificate Rackspace Rackspace Cloud Servers DreamHost DreamHost Log Hosting