features 0.5.12

Links

• GitHub: https://github.com/xflr6/features

• PyPI: https://pypi.org/project/features/

• Documentation: https://features.readthedocs.io

• Changelog: https://features.readthedocs.io/en/latest/changelog.html

• Issue Tracker: https://github.com/xflr6/features/issues

• Download: https://pypi.org/project/features/#files

Installation

This package runs under Python 2.7 and 3.5+, use pip to install:

$ pip install features

This will also install the concepts package from PyPI providing the Formal Concept Analysis (FCA) algorithms on which this package is based.

Quickstart

Load a predefined feature system by name (in this case features for a six-way person/number distinction, cf. the definitions in the bundled config.ini in the source repository).

>>> import features

>>> fs = features.FeatureSystem('plural')

>>> print(fs.context)  # doctest: +ELLIPSIS
<Context object mapping 6 objects to 10 properties [3011c283] at 0x...>
      |+1|-1|+2|-2|+3|-3|+sg|+pl|-sg|-pl|
    1s|X |  |  |X |  |X |X  |   |   |X  |
    1p|X |  |  |X |  |X |   |X  |X  |   |
    2s|  |X |X |  |  |X |X  |   |   |X  |
    2p|  |X |X |  |  |X |   |X  |X  |   |
    3s|  |X |  |X |X |  |X  |   |   |X  |
    3p|  |X |  |X |X |  |   |X  |X  |   |

Create feature sets from strings or string sequences. Use feature string parsing, get back string sequences and feature or extent strings in their canonical order (definition order):

>>> fs('+1 +sg'), fs(['+2', '+2', '+sg']), fs(['+sg', '+3'])
(FeatureSet('+1 +sg'), FeatureSet('+2 +sg'), FeatureSet('+3 +sg'))

>>> fs('SG1').concept.intent
('+1', '-2', '-3', '+sg', '-pl')

>>> fs('1').string, fs('1').string_maximal, fs('1').string_extent
('+1', '+1 -2 -3', '1s 1p')

Use feature algebra: intersection (join) , union/unification (meet), set inclusion (extension/subsumption). Do feature set comparisons (logical connectives).

>>> fs('+1 +sg') % fs('+2 +sg')
FeatureSet('-3 +sg')

>>> fs('-3') ^ fs('+1') ^ fs('-pl')
FeatureSet('+1 +sg')

>>> fs('+3') > fs('-1') and fs('+pl') < fs('+2 -sg')
True

>>> fs('+1').incompatible_with(fs('+3')) and fs('+sg').complement_of(fs('+pl'))
True

Navigate the created subsumption lattice (Hasse graph) of all valid feature sets:

>>> fs('+1').upper_neighbors, fs('+1').lower_neighbors
([FeatureSet('-3'), FeatureSet('-2')], [FeatureSet('+1 +sg'), FeatureSet('+1 +pl')])

>>> fs('+1').upset()
[FeatureSet('+1'), FeatureSet('-3'), FeatureSet('-2'), FeatureSet('')]

>>> for f in fs:  # doctest: +ELLIPSIS
...     print('[%s] <-> {%s}' % (f.string_maximal, f.string_extent))
[+1 -1 +2 -2 +3 -3 +sg +pl -sg -pl] <-> {}
[+1 -2 -3 +sg -pl] <-> {1s}
...
[-1] <-> {2s 2p 3s 3p}
[] <-> {1s 1p 2s 2p 3s 3p}

See the docs on how to define, load, and use your own feature systems.

Further reading

• https://en.wikipedia.org/wiki/Join_and_meet

• https://en.wikipedia.org/wiki/Formal_concept_analysis

• http://www.upriss.org.uk/fca/

See also

• concepts – Formal Concept Analysis with Python

• fileconfig – Config file sections as objects

• graphviz – Simple Python interface for Graphviz

License

Features is distributed under the MIT license.