boolexp 0.1

Safe boolean expression evaluator

Boolexp provides “safe” evaluation of boolean expressions for use cases where eval might be dangerous. Boolexp expressions are context-free and mimic Python sytax. Only basic math opearations and data structures are provided.

Instalation

To install Boolexp, change to the directory where setup.py is located and type:

python setup.py install

Requirements:

• Python 2.7

• pyparsing 1.5.0 or later

Expression Syntax Overview

Basic math operators *,/,+,- have highest priority

>>> from boolexp import Expression
>>> Expression("4 + 4 / 2").evaluate()
>>> 6
>>> Expression("( 4 + 4 ) / 2 ").evaluate()
>>> 4

Comparsion operators !=, ==, <, >, <=, >=, in are next in priority. All comparsion operators have return type of boolean, which can be used as input for boolean operators and, or, not with lowest priority.

>>> from boolexp import Expression
>>> Expression(2 == 1).evaluate()
>>> False
>>> Expression("2 * - 2 == - 4").evaluate()
>>> True
>>> Expression("not 2 == 3").evaluate()
>>> True
>>> Expression("3 <= 8 and 2 == 5").evaluate()
>>> False

Expresions with with variables

This all would not be much of a fun without posibility to use variables. Allowed types for variables are bool,int,float,str,list,dict

>>> from boolexp import Expression
>>> Expression("1 in v").evaluate(dict(v=[1,2])).evaluate()
>>> True
>>> Expression("one[1].part == 2").evaluate(dict(one=[1, dict(part=2)], two=1)).evaluate()
>>> True

Diclaimer

This project is now in a state of proof of concept only, thus far from suitable for production enviroment.