rule-engine 4.5.3
A lightweight, optionally typed expression language with a custom grammar for matching arbitrary Python objects.
License: BSD

Rule Engine
===========
|badge-build| |badge-pypi|

A lightweight, optionally typed expression language with a custom grammar for matching arbitrary Python objects.

Documentation is available at https://zeroSteiner.github.io/rule-engine/.

:Warning:
  The next major version (5.0) will remove support Python versions 3.6, 3.7 and 3.8. There is currently no timeline for
  its release.

Rule Engine expressions are written in their own language, defined as strings in Python. The syntax is most similar to
Python with some inspiration from Ruby. Some features of this language includes:

- Optional type hinting
- Matching strings with regular expressions
- Datetime datatypes
- Compound datatypes (equivalents for Python dict, list and set types)
- Data attributes
- Thread safety

Example Usage
-------------
The following example demonstrates the basic usage of defining a rule object and applying it to two dictionaries,
showing that one matches while the other does not. See `Getting Started`_ for more information.

.. code-block:: python

   import rule_engine
   # match a literal first name and applying a regex to the email
   rule = rule_engine.Rule(
       'first_name == "Luke" and email =~ ".*@rebels.org$"'
   ) # => <Rule text='first_name == "Luke" and email =~ ".*@rebels.org$"' >
   rule.matches({
       'first_name': 'Luke', 'last_name': 'Skywalker', 'email': 'luke@rebels.org'
   }) # => True
   rule.matches({
      'first_name': 'Darth', 'last_name': 'Vader', 'email': 'dvader@empire.net'
   }) # => False

The next example demonstrates the optional type system. A custom context is created that defines two symbols, one string
and one float. Because symbols are defined, an exception will be raised if an unknown symbol is specified or an invalid
operation is used. See `Type Hinting`_ for more information.

.. code-block:: python

   import rule_engine
   # define the custom context with two symbols
   context = rule_engine.Context(type_resolver=rule_engine.type_resolver_from_dict({
       'first_name': rule_engine.DataType.STRING,
       'age': rule_engine.DataType.FLOAT
   }))

   # receive an error when an unknown symbol is used
   rule = rule_engine.Rule('last_name == "Vader"', context=context)
   # => SymbolResolutionError: last_name

   # receive an error when an invalid operation is used
   rule = rule_engine.Rule('first_name + 1', context=context)
   # => EvaluationError: data type mismatch

Want to give the rule expression language a try? Checkout the `Debug REPL`_ that makes experimentation easy. After
installing just run ``python -m rule_engine.debug_repl``.

Installation
------------
Install the latest release from PyPi using ``pip install rule-engine``. Releases follow `Semantic Versioning`_ to
indicate in each new version whether it fixes bugs, adds features or breaks backwards compatibility. See the
`Change Log`_ for a curated list of changes.

Credits
-------
* Spencer McIntyre - zeroSteiner |social-github|

License
-------
The Rule Engine library is released under the BSD 3-Clause license. It is able to be used for both commercial and
private purposes. For more information, see the `LICENSE`_ file.

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   :alt: GitHub Workflow Status (branch)
   :target: https://github.com/zeroSteiner/rule-engine/actions/workflows/ci.yml

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   :target: https://pypi.org/project/rule-engine/

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.. _Change Log: https://zerosteiner.github.io/rule-engine/change_log.html
.. _Debug REPL: https://zerosteiner.github.io/rule-engine/debug_repl.html
.. _Getting Started: https://zerosteiner.github.io/rule-engine/getting_started.html
.. _LICENSE: https://github.com/zeroSteiner/rule-engine/blob/master/LICENSE
.. _Semantic Versioning: https://semver.org/
.. _Type Hinting: https://zerosteiner.github.io/rule-engine/getting_started.html#type-hinting