Orderly Set 5.2.3

Orderly Set is a package containing multiple implementations of Ordered Set.

OrderlySet

This implementation keeps the order in all set operations except set difference operations. As a result, it can do set difference operations much faster than other implementations. Still 2X slower than of Python's built-in set.

StableSet

A StableSet is a mutable set that remembers its insertion order. Featuring: Fast O(1) insertion, deletion, iteration and membership testing. But slow O(N) Index Lookup.

StableSetEq

Same as StableSet but the order of items doesn't matter for equality comparisons.

OrderedSet

An OrderedSet is a mutable data structure that is a hybrid of a list and a set. It remembers its insertion order so that every entry has an index that can be looked up. Featuring: O(1) Index lookup, insertion, iteration and membership testing. But slow O(N) Deletion.

SortedSet

SortedSet is basically set but when printed, turned into string, or iterated over, returns the items in alphabetical order.

Installation

pip install orderly-set

Usage examples

An OrderedSet is created and used like a set:

>>> from orderly_set import OrderedSet

>>> letters = OrderedSet('abracadabra')

>>> letters
OrderedSet(['a', 'b', 'r', 'c', 'd'])

>>> 'r' in letters
True

It is efficient to find the index of an entry in an OrderedSet, or find an entry by its index. To help with this use case, the .add() method returns the index of the added item, whether it was already in the set or not.

>>> letters.index('r')
2

>>> letters[2]
'r'

>>> letters.add('r')
2

>>> letters.add('x')
5

OrderedSets implement the union (|), intersection (&), and difference (-) operators like sets do.

>>> letters |= OrderedSet('shazam')

>>> letters
OrderedSet(['a', 'b', 'r', 'c', 'd', 'x', 's', 'h', 'z', 'm'])

>>> letters & set('aeiou')
OrderedSet(['a'])

>>> letters -= 'abcd'

>>> letters
OrderedSet(['r', 'x', 's', 'h', 'z', 'm'])

The __getitem__() and index() methods have been extended to accept any iterable except a string, returning a list, to perform NumPy-like "fancy indexing".

>>> letters = OrderedSet('abracadabra')

>>> letters[[0, 2, 3]]
['a', 'r', 'c']

>>> letters.index(['a', 'r', 'c'])
[0, 2, 3]

OrderedSet implements __getstate__ and __setstate__ so it can be pickled, and implements the abstract base classes collections.MutableSet and collections.Sequence.

OrderedSet can be used as a generic collection type, similar to the collections in the typing module like List, Dict, and Set. For example, you can annotate a variable as having the type OrderedSet[str] or OrderedSet[Tuple[int, str]].

Authors

Please check the Authors file.

Comparisons

-- initialize a set --
Using Python dict time: 4.13
set time: 2.98
ordered_set.OrderedSet time: 15.77
orderly_set.OrderedSet time: 15.25
StableSet time: 4.78
OrderlySet time: 4.38
SortedSet time: 3.09

-- update a set --
Using Python dict: 6.77
set time: 2.46
ordered_set.OrderedSet time: 10.17
orderly_set.OrderedSet time: 10.06
StableSet time: 7.16
OrderlySet time: 6.77
SortedSet time: 2.46

-- update a set and get item --
ordered_set.OrderedSet time: 29.98
orderly_set.OrderedSet time: 29.57
StableSet time: 14.31
OrderlySet time: 14.23
SortedSet time: 9.03

-- set symmetric difference (xor) --
set time: 5.368663903005654
ordered_set.OrderedSet time: 39.25
orderly_set.OrderedSet time: 80.31
StableSet time: 42.81
OrderlySet time: 11.44
SortedSet time: 3.87

-- set difference (-) --
set time: 3.7398674299911363
ordered_set.OrderedSet time: 22.39
orderly_set.OrderedSet time: 38.00
StableSet time: 22.30
OrderlySet time: 8.92
SortedSet time: 3.03

Despite what you see in the benchmarks, in DeepDiff OrderlySet performed better than SortedSet.

A StableSet is a mutable set that remembers its insertion order. Featuring: Fast O(1) insertion, deletion, iteration and membership testing. But slow O(N) Index Lookup.

An OrderedSet is a mutable data structure that is a hybrid of a list and a set. It remembers its insertion order so that every entry has an index that can be looked up. Featuring: O(1) Index lookup, insertion, iteration and membership testing. But slow O(N) Deletion.

Both have similar interfaces but differ in respect of their implementation and performance.

The original implementation of OrderedSet was a recipe posted to ActiveState Recipes by Raymond Hettiger, released under the MIT license.

Hettiger's implementation kept its content in a doubly-linked list referenced by a dict. As a result, looking up an item by its index was an O(N) operation, while deletion was O(1).

This version of OrderedSet makes different trade-offs for the sake of efficient lookups. Its content is a standard Python list instead of a doubly-linked list. This provides O(1) lookups by index at the expense of O(N) deletion, as well as slightly faster iteration.