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rules-engine

This project implement a rules-engine.

Example of rules:

Either:
  credit_rating is above 50
  AND
  flood_risk is below 10
OR
  revenue is above 1000000

Requirements

These rules need to be configurable and variable in several ways:

  • The number of comparisons
  • The variables referenced (e.g. replacing credit_rating with something else)
  • The constant values being compared against
  • The operators being used (e.g. greater than, less than, equals)
  • The structure of the boolean composition (i.e where AND/OR/etc are, and where the parentheses are)

Implementation

The imput should be like this:

EXAMPLE_1 = {
    "credit_rating": 75,
    "flood_risk": 5,
    "revenue": 1000
}

And the output, following the rules above, in this case will return:

True

Technologies

  • Python3
  • pytest

Data Structure

  • Binary Tree

Init

To install the dependences, open a terminal from the main folder.

Create a virtual env: py -m venv env

Acrivate the virtual env. Linux: source env/bin/activate Windows: source env/bin/activate

Install the dependencies: pip install -r requirements.txt If problems, try eith: python -m pip install -r requirements.txt

The only dependency to be installed is pytest. I chose it because it is the most commonly used Python library for tests.

To run the program, you can just run (outside env) the main.py. To run the tests (outside env): pytest test.py

There is a default Rule but you can change it. To change, when you run main .py, answer with "y" to the question about changing the rule. The Role data structure is a binary tree, so you have to put the right side and left side of the comparision. When you define a rule, need to define the operator or comparator, variable name end value of the comparator. Operator can be AND, OR or XOR defined as follows: and_ -> AND or_ -> OR xor -> XOR Comparator can be <, <=, ==, !=, >=, > defined as follows: lt -> < le -> <= eq -> == ne -> != ge -> >= gt -> >

So, if you want to define a rule like:

Either:
  credit_rating is above 50
  AND
  flood_risk is below 10
OR
  revenue is above 1000000

You will follow those steps: Do you want to change the rule? (y or n) y Insert new Rule operator or comparator: or_ Insert left side Insert new Rule operator or comparator: and_ Insert left side Insert new Rule operator or comparator: gt Insert left side credit_rating Insert right side 50 Insert right side Insert new Rule operator or comparator: lt Insert left side flood_risk Insert right side 10 Insert right side: Insert new Rule operator or comparator: gt Insert the left Side revenue Insert the right side 1000000

Then, need to define data. The system will ask you if do you want to add a new variable. For this variable you need the put name and value. For example, if you want to put input data like those:

EXAMPLE_1 = {
    "credit_rating": 75,
    "flood_risk": 5,
    "revenue": 1000
}

You will follow those steps:

Put your data Variable name: credit_rating Variable value: 55 Do you want to add other variables? (y or n) y Variable name: flood_risk Variable value: 5 Do you want to add other variables? (y or n) y Variable name: revenue Variable value: 1000

Missing variables are considered with value = 0.