Metadata-Version: 2.1
Name: business-rule-engine
Version: 0.1.2
Summary: Python DSL for setting up business intelligence rules
Home-page: https://github.com/manfred-kaiser/business-rule-engine
Author: Manfred Kaiser
Author-email: manfred.kaiser@logfile.at
License: UNKNOWN
Project-URL: Source, https://github.com/manfred-kaiser/business-rule-engine
Project-URL: Tracker, https://github.com/manfred-kaiser/business-rule-engine/issues
Description: business-rule-engine
        ====================
        
        [![CodeFactor](https://www.codefactor.io/repository/github/manfred-kaiser/business-rule-engine/badge)](https://www.codefactor.io/repository/github/manfred-kaiser/business-rule-engine)
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        As a software system grows in complexity and usage, it can become burdensome if every change to the logic/behavior of the system also requires you to write and deploy new code. The goal of this business rules engine is to provide a simple interface allowing anyone to capture new rules and logic defining the behavior of a system, and a way to then process those rules on the backend.
        
        You might, for example, find this is a useful way for analysts to define marketing logic around when certain customers or items are eligible for a discount or to automate emails after users enter a certain state or go through a particular sequence of events.
        
        ## Usage
        
        ### 1. Define Your set of variables
        
        Variables represent values in your system, usually the value of some particular object.  You create rules by setting threshold conditions such that when a variable is computed that triggers the condition some action is taken.
        
        ```python
        params = {
            'products_in_stock': 10
        }
        ```
        
        ### 2. Define custom functions
        
        ```python
        def order_more(items_to_order):
            print("you ordered {} new items".format(items_to_order))
            return items_to_order
        ```
        
        ### 3. Write the rules
        
        
        ```python
        rules = """
        rule "order new items"
        when
            products_in_stock < 20
        then
            order_more(50)
        end
        """
        ```
        
        ### 3. Create the parser and parse the rule
        
        ```python
        from business_rule_engine import RuleParser
        
        parser = RuleParser()
        parser.register_function(order_more)
        parser.parsestr(rules)
        parser.execute(params)
        ```
        
        ## Supported functions
        
        Business rule engine uses Excel like functions (thanks to [formulas](https://github.com/vinci1it2000/formulas). So it is possible to use most of them in rules.
        
        
        ## Multiple conditions and multiple actions
        
        You can make multiple checks on the same params, and call multiple actions as needed:
        
        ```python
        rules = """
        rule "order new items"
        when
            AND(products_in_stock < 20,
            products_in_stock >= 5)
        then
            order_more(50)
        end
        
        rule "order new items urgent"
        when
            products_in_stock < 5,
        then
            AND(order_more(10, true),
            order_more(50))
        end
        """
        ```
        
        ## Custom functions
        
        You can also write your own functions to validate conditions and use other libraries functions as actions:
        
        ```python
        from business_rule_engine import RuleParser
        
        def is_even(num):
           if (num % 2) == 0:
              return True
           return False
        
        params = {
            'number': 10
        }
        
        rules = """
        rule "check even number"
        when
            is_even(number) = True
        then
            print("is even")
        end
        """
        
        parser = RuleParser()
        parser.register_function(is_even)
        parser.register_function(print)
        parser.parsestr(rules)
        parser.execute(params)
        
        ```
        
        ## Handle missing rule parameters
        
        If some argruments are missing, the rule engine will raise a ValueError.
        
        There are some use cases, when you have to work with incomplete data. In such cases, you can define
        default arguments.
        
        You enable default rule arguments with the parameter `set_defaule_arg`. The default argument will have the Value `None`. To provide another value you can use `default_arg`.
        
        ```python
        params = {}
        
        rules = """
        rule "order new items"
        when
            products_in_stock < 20
        then
            order_more(50)
        end
        """
        
        parser = RuleParser()
        parser.register_function(order_more)
        parser.parsestr(rules)
        parser.execute(params, set_default_arg=True, default_arg=0)
        ```
        
        ## More control of the RulePraser
        
        if you need more control, how the rule parser handles rules, you can iterate over the parser and execute each rule in your script.
        
        This gives you more control on how to handle missing arguments, rules with errors and you have access to the return values of the conditions and the actions.
        
        ```python
        from business_rule_engine import RuleParser
        from business_rule_engine.exceptions import MissingArgumentError
        
        def order_more(items_to_order):
            return "you ordered {} new items".format(items_to_order)
        
        rules = """
        rule "order new items"
        when
            products_in_stock < 20
        then
            order_more(50)
        end
        """
        
        params = {
            'products_in_stock': 10
        }
        
        parser = RuleParser()
        parser.register_function(order_more)
        parser.parsestr(rules)
        for rule in parser:
            try:
                rvalue_condition, rvalue_action = rule.execute(params)
                if rule.status:
                    print(rvalue_action)
                    break
            except MissingArgumentError:
                pass
        ```
        
        
        ## Error Handling
        
        Most of the errors are caused by missing parameters, you can handle the errors and interpret the results handling ValueError:
        
        ```python
        from business_rule_engine import RuleParser
        
        # proposital typo
        params = {
            'produtcs_in_stock': 30
        }
        
        rules = """
        rule "order new items"
        when
            products_in_stock < 20
        then
            order_more(50)
        end
        """
        
        parser = RuleParser()
        parser.register_function(order_more)
        parser.parsestr(rules)
        try:
            ret = parser.execute(params)
            if ret is False:
                print("No conditions matched")
        except ValueError as e:
            print(e)
        ```
        
        ## Debug
        
        To debug the rules processing, use the logging lib.
        
        You can insert in your Python script to log to stdout:
        ```
        import logging
        logging.basicConfig(stream=sys.stdout, level=logging.DEBUG)
        ```
        
Keywords: business rules engine
Platform: UNKNOWN
Classifier: Programming Language :: Python :: 3
Classifier: Programming Language :: Python :: 3.6
Classifier: Programming Language :: Python :: 3.7
Classifier: Programming Language :: Python :: 3.8
Requires-Python: >= 3.6
Description-Content-Type: text/markdown
