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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 and 3.7. 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:
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
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
context = rule_engine.Context(type_resolver=rule_engine.type_resolver_from_dict({ 'first_name': rule_engine.DataType.STRING, 'age': rule_engine.DataType.FLOAT }))
rule = rule_engine.Rule('last_name == "Vader"', context=context)
rule = rule_engine.Rule('first_name + 1', context=context)
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.
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.
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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.. _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