Metadata-Version: 2.1
Name: ordered-set
Version: 4.1.0
Summary: A set that remembers its order, and allows looking up its items by their index in that order.
Home-page: https://github.com/rspeer/ordered-set
Author: Elia Robyn Lake
Author-email: Elia Robyn Lake <gh@arborelia.net>
License: Copyright (c) 2012-2022 Elia Robyn Lake
        
        Permission is hereby granted, free of charge, to any person obtaining a
        copy of this software and associated documentation files (the "Software"),
        to deal in the Software without restriction, including without limitation
        the rights to use, copy, modify, merge, publish, distribute, sublicense,
        and/or sell copies of the Software, and to permit persons to whom the
        Software is furnished to do so, subject to the following conditions:
        
        The above copyright notice and this permission notice shall be included in
        all copies or substantial portions of the Software.
        
        THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
        IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
        FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
        AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
        LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
        FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
        DEALINGS IN THE SOFTWARE.
        
Project-URL: Home, https://github.com/rspeer/ordered-set
Classifier: Development Status :: 5 - Production/Stable
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: MIT License
Classifier: Programming Language :: Python
Classifier: Programming Language :: Python :: 3
Classifier: Programming Language :: Python :: 3.7
Classifier: Programming Language :: Python :: 3.8
Classifier: Programming Language :: Python :: 3.9
Classifier: Programming Language :: Python :: 3.10
Classifier: Programming Language :: Python :: Implementation :: CPython
Classifier: Programming Language :: Python :: Implementation :: PyPy
Requires-Python: >=3.7
Description-Content-Type: text/markdown
Provides-Extra: dev
Requires-Dist: pytest; extra == "dev"
Requires-Dist: black; extra == "dev"
Requires-Dist: mypy; extra == "dev"

[![Pypi](https://img.shields.io/pypi/v/ordered-set.svg)](https://pypi.python.org/pypi/ordered-set)

An OrderedSet is a mutable data structure that is a hybrid of a list and a set.
It remembers the order of its entries, and every entry has an index number that
can be looked up.

## Installation

`ordered_set` is available on PyPI and packaged as a wheel. You can list it
as a dependency of your project, in whatever form that takes.

To install it into your current Python environment:

    pip install ordered-set

To install the code for development, after checking out the repository:

    pip install flit
    flit install

## Usage examples

An OrderedSet is created and used like a set:

    >>> from ordered_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]]`.


## OrderedSet in data science applications

An OrderedSet can be used as a bi-directional mapping between a sparse
vocabulary and dense index numbers. As of version 3.1, it accepts NumPy arrays
of index numbers as well as lists.

This combination of features makes OrderedSet a simple implementation of many
of the things that `pandas.Index` is used for, and many of its operations are
faster than the equivalent pandas operations.

For further compatibility with pandas.Index, `get_loc` (the pandas method for
looking up a single index) and `get_indexer` (the pandas method for fancy
indexing in reverse) are both aliases for `index` (which handles both cases
in OrderedSet).


## Authors

OrderedSet was implemented by Elia Robyn Lake (maiden name: Robyn Speer).
Jon Crall contributed changes and tests to make it fit the Python set API.
Roman Inflianskas added the original type annotations.


## Comparisons

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

[recipe]: https://code.activestate.com/recipes/576694-orderedset/

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 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.

In Python 3.6 and later, the built-in `dict` type is inherently ordered. If you
ignore the dictionary values, that also gives you a simple ordered set, with
fast O(1) insertion, deletion, iteration and membership testing. However, `dict`
does not provide the list-like random access features of OrderedSet. You
would have to convert it to a list in O(N) to look up the index of an entry or
look up an entry by its index.
