python business_rules package example

business_rules_example.py

# pip install business-rules

from decimal import Decimal
from pprint import pprint

from business_rules import (
    variables, actions, fields, export_rule_data, run_all
)


class Request(object):
    def __init__(self, contractor, cart):
        self.contractor = contractor
        self.cart = cart


class Contractor(object):
    def __init__(self, symbol):
        self.symbol = symbol


class Cart(object):
    def __init__(self, total):
        self.total = total

    def get_total(self):
        return self.total


class PaymentMethod(object):
    def __init__(self, symbol, gateway_symbol, amount, is_active):
        self.symbol = symbol
        self.gateway_symbol = gateway_symbol
        self.amount = amount
        self.is_active = is_active


class PaymentMethodVariables(variables.BaseVariables):

    def __init__(self, request, method):
        self.method = method
        self.request = request

    @variables.string_rule_variable()
    def current_contractor(self):
        return getattr(self.request.contractor, 'symbol')

    @variables.string_rule_variable()
    def method_symbol(self):
        return self.method.symbol

    @variables.string_rule_variable()
    def gateway_symbol(self):
        return self.method.gateway.symbol

    @variables.numeric_rule_variable()
    def cart_total(self):
        return self.request.cart.get_total()


class PaymentMethodActions(actions.BaseActions):
    def __init__(self, request, method):
        self.method = method
        self.request = request

    @actions.rule_action(params={
        'active': fields.FIELD_SELECT_MULTIPLE
    })
    def change_active(self, active):
        self.method.is_active = active

    @actions.rule_action(params={
        'amount': fields.FIELD_NUMERIC,
    })
    def set_amount(self, amount):
        self.method.amount = amount


if __name__ == '__main__':
    request = Request(Contractor('stefan'), Cart(Decimal('101')))
    method = PaymentMethod('cash', 'general', Decimal('1.12'), True)

    rules = export_rule_data(PaymentMethodVariables, PaymentMethodActions)
    pprint(rules)

    run_all(
        rule_list=[
            {
                'conditions': {
                    'all': [
                        {
                            'name': 'current_contractor',
                            'operator': 'equal_to',
                            'value': 'stefan',
                        },
                    ],
                },
                'actions': [
                    {
                        'name': 'change_active',
                        'params': {
                            'active': False,
                        },
                    },
                ]
            },
            {
                'conditions': {
                    'all': [
                        {
                            'name': 'cart_total',
                            'operator': 'greater_than',
                            'value': Decimal('100'),
                        },
                    ],
                },
                'actions': [
                    {
                        'name': 'change_active',
                        'params': {
                            'active': True,
                        },
                    },
                    {
                        'name': 'set_amount',
                        'params': {
                            'amount': Decimal('0'),
                        },
                    },
                ]
            },
        ],
        defined_variables=PaymentMethodVariables(request, method),
        defined_actions=PaymentMethodActions(request, method),
        stop_on_first_trigger=False
    )
    pprint(method.__dict__)

That's great :) you welcome.