experta 1.9.3

Expert Systems for Python

Experta is a Python library for building expert systems strongly inspired by CLIPS.

from random import choice
from experta import *


class Light(Fact):
    """Info about the traffic light."""
    pass


class RobotCrossStreet(KnowledgeEngine):
    @Rule(Light(color='green'))
    def green_light(self):
        print("Walk")

    @Rule(Light(color='red'))
    def red_light(self):
        print("Don't walk")

    @Rule(AS.light << Light(color=L('yellow') | L('blinking-yellow')))
    def cautious(self, light):
        print("Be cautious because light is", light["color"])

>>> engine = RobotCrossStreet()
>>> engine.reset()
>>> engine.declare(Light(color=choice(['green', 'yellow', 'blinking-yellow', 'red'])))
>>> engine.run()
Be cautious because light is blinking-yellow

Migrating from Pyknow

Experta is a Pyknow fork. Just replace any pyknow references in your code/examples to experta and everything should work the same.

Examples

You can find some more examples on GitHub.

TODO

CHANGELOG

1.9.3

• Resolve #11 that was introduced with #7, that caused the same behavior under different conditions.

1.9.2

• Resolved #7. In some situations last activation was removed right after entering the agenda.

1.9.1

• Resolved #3. Rules should not be called with already retracted facts.

1.9.0

• Drop Python 3.4 support.

• Use setup.cfg to save all package metadata.

1.8.0-1.8.2

• Rebranded to Experta.

1.7.0

• Implemented the template system.

• Replaced warnings by watchers messages.

• Fixed freeze() with frozen objects.

• Fixed unfreeze() with unfrozen objects.

• Parametrized DefFacts via reset() kwargs.

1.6.0

• Improved overall performance.

1.5.0

• Added Python version 3.7 to tox.ini.

• Monkey and bananas example.

• Fixed bug, numeric index args gets repeated in a weird way introduced in 1.4.0.

• Pass only the defined args in absence of kwargs.

1.4.0

• Order integer facts keys after making a copy.

• as_dict method for Fact.

• freeze and unfreeze method documentation.

• unfreeze method in pyknow.utils.

• Zebra example from Clips.

1.3.0

• pyknow.operator module.

• Nested matching.

• Added Talk ‘Sistemas Expertos en Python con PyKnow - PyConES 2017’ to docs folder.

1.2.0

• Freeze fact values as the default behavior to address Issue #9.

• Added pyknow.utils.anyof to mitigate Issue #7.

• Raise RuntimeError if a fact value is modified after declare().

• Added MATCH and AS objects.

1.1.1

• Removing the borg optimization for P field constraints.

• Use the hash of the check in the sorting of the nodes to always generate the same alpha part of the network.

1.1.0

• Allow any kind of callable in Predicate Field Constraints (P()).

1.0.1

• DNF of OR clause inside AND or Rule was implemented wrong.

1.0.0

• RETE matching algorithm.

• Better Rule decorator system.

• Facts are dictionaries.

• Documentation.

<1.0.0

• Unestable API.

• Wrong matching algorithm.

• Bad performance

• PLEASE DON’T USE THIS.