kharazmi 0.1.4

An equation parser/calculator module for python.

Kharazmi

Kharazmi, persian pronunciation of Khwarizmi (al-Khwarizmi, Algorithmi), is an equation parser/calculator module for python.

It's main purpose is to provide an easy method to get equations from user and run them on your own data without using eval and having the freedom of using it on different data types (number, numpy arrays, etc.)

Currently it supports:

• Basic math operations (+-*/^)
• Numeric Variables (int, float, complex)
• Plugable functions

Installation

Simply install using pip:

pip install kharazmi

Keep in mind that Kharazmi uses Python type annotations (PEP 484), and f-Strings (PEP 498) so you'll need Python 3.6 or higher.

Usage

Basic Usage

Kharazmi provides a simple yet powerful API. First of all you have EquationParser, the core of the Kharazmi. It's the main class that you need to worry about. Simply instantiate it and pass your user's input to its parse method:

from kharazmi import EquationParser

parser = EquationParser()

user_input = "2*x / (2 - y)"

expression = parser.parse(user_input)

All expressions are subclass of kharazmi.models.BaseNumericalExpression class. You can work with them as if they were python variables containing integers, e.g:

expression1 = parser.parse("3*x - y")
expression2 = parser.parse("z")

expression3 = expression1 / expression2

You can even build your expressions using normal python code:

x = parser.parse("x")

expression4 = 2*x + 4

BaseNumericalExpression class provides a evaluate method. It allows you to evaluate value of an expression given the values you provides for variables:

expression5 = parser.parse("2*x + 4")

expression5.evaluate(x=2)

Because Kharazmi uses python mathematical operators (+-*/^) under the hood, you can pass any value that supports these operations and still get the correct result, e.g: you can pass numpy arrays:

import numpy as np

expression6 = parser.parse("2*x + y")

x = np.ones((2,2))
y = np.identity(2)

expression6.evaluate(x=x, y=y)

Finally, if you have an expression which you don't know its variables, you can get a list of them using variables property of the expression.

Using functions

What if you want to create a more complex expressions, like sin(x)^2 + cos(x)^2.

Well, first of all, you'll have to tell kharazmi the list of your functions:

from math import sin, cos

from kharazmi import register_function

register_function("sin", sin)
register_function("cos", cos)

expression7 = parser.parse("sin(x)^2 + cos(x)^2")

You can even have functions with multiple inputs:

register_function("min", min)

expression7 = parser.parse("1 + min(x, y)")

If you want to use python's builtin math function, you can use kharazmi.activate_builtin_math. Calling this function will register all builtin functions from math, along with min, max, round, and abs.

from kharazmi import activate_builtin_math

activate_builtin_math()

expression8 = parser.parse("log2(8)")

Using as a module

You can run kharazmi as a module using python -m kharazmi, this will run a REPL like program that lets you enter expressions, see how you can do the same thing in code, in other words how kharazmi is understanding your input, and evaluate it.

It supports all math function either.

It's mostly for debugging and testing purposes, but it's there if you want to understand how kharazmi is working, I suggest start from there.