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:
Version 6.0 will remove support for Python version 3.10. There is currently no timeline for its release.
:Warning:
Version 5.0 removes support for Python versions 3.6, 3.7, 3.8, and 3.9 and deprecates attribute-style access on
MAPPING values (use bracket syntax mapping["key"] instead). See the Change Log_ for details.
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
- Rule chains that return the value of the first matching rule
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.matches({
'first_name': 'Luke', 'last_name': 'Skywalker', 'email': '[email protected]'
}) # => True
rule.matches({
'first_name': 'Darth', 'last_name': 'Vader', 'email': '[email protected]'
}) # => 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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.. _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
