Does Python have an ordered set?

Question

Python has an ordered dictionary. What about an ordered set?

Answer 1

If you're using the ordered set to maintain a sorted order, consider using a sorted set implementation from PyPI. The sortedcontainers module provides a SortedSet for just this purpose. Some benefits: pure-Python, fast-as-C implementations, 100% unit test coverage, hours of stress testing.

Installing from PyPI is easy with pip:

pip install sortedcontainers

Note that if you can't pip install, simply pull down the sortedlist.py and sortedset.py files from the open-source repository.

Once installed you can simply:

from sortedcontainers import SortedSet
help(SortedSet)

The sortedcontainers module also maintains a performance comparison with several alternative implementations.

For the comment that asked about Python's bag data type, there's alternatively a SortedList data type which can be used to efficiently implement a bag.