Simple Rule engine in pure Python

This rule engine allows for the creation and combination of (nested) rules.

Inspired by the behavior of Django's Q object, this rule engine allows for the creation of complex rules that can be evaluated with a dictionary of values.

A Rule object is a class that can be initiated wit more Rule objects as positional *args and **kwargs for additional conditions.

Supported operators are: gte, lte, gt, lt, ne, in, contains, icontains, exact, iexact, startswith, endswith.

More can be added if you are bored enough.

The Rule object can be combined with & (and), | (or).

~~Currently, the ~ (not) operator is not supported but it can be added~~. I had an after dinner urge to implement it because it was just a few lines of code.

The Rule object can be evaluated with a dictionary of values:

from rule_engine import Rule, evaluate

r = Rule(
    Rule(foo="bar") | Rule(foo="baz"),
    name="John", age__gte=21
) | Rule(
    name="Jane", age__lt=20
)

example_true = {"foo": "bar", "name": "John", "age": 22}
print(evaluate(r, example_true))  # True

See src/solution.py for more examples.

The provided rule in the example would translate to:

provided_rule = Rule(
    credit_rating__gt=50,
    flood_risk__lt=10,
) | Rule(revenue__gt=1_000_000)
# Rule(conditions=[('AND', Rule(conditions=[('AND', {'credit_rating__gt': 50, 'flood_risk__lt': 10})], negated=False)), ('OR', Rule(conditions=[('AND', {'revenue__gt': 1000000})], negated=False))], negated=False)

Of course this is not a full-fledged rule engine, so there is very lacking exception handling and error messages.

Ngl, it was fun to write this. I'm gonna use it for something, I'm sure.

biagiodistefano/rule-engine

Simple Rule engine in pure Python