Python Mathematical Expression Evaluator

Based on js-expression-eval, by Matthew Crumley ([email protected], http://silentmatt.com/) https://github.com/silentmatt/js-expression-eval

Ported to Python and modified by Vera Mazhuga ([email protected], http://vero4ka.info/)

You are free to use and modify this code in anyway you find useful. Please leave this comment in the code to acknowledge its original source. If you feel like it, I enjoy hearing about projects that use my code, but don't feel like you have to let me know or ask permission.

Installation

pip install py_expression_eval

Examples

parser = Parser()
parser.parse('2 * 3').evaluate({})  # 6
parser.parse('2 ^ x').evaluate({'x': 3})  # 8
parser.parse('2 * x + 1').evaluate({'x': 3})  # 7
parser.parse('2 + 3 * x').evaluate({'x': 4})  # 14
parser.parse('(2 + 3) * x').evaluate({'x': 4}) # 20
parser.parse('2-3^x').evaluate({'x': 4})  # -79
parser.parse('-2-3^x').evaluate({'x': 4})  # -83
parser.parse('-3^x').evaluate({'x': 4})  # -81
parser.parse('(-3)^x').evaluate({'x': 4})  # 81
parser.parse('2*x + y').evaluate({'x': 4, 'y': 1})  # 9
parser.parse('round(log(2.7))').evaluate({}) # 1

# substitute
expr = parser.parse('2 * x + 1')
expr2 = expr.substitute('x', '4 * x')  # ((2*(4*x))+1)
expr2.evaluate({'x': 3})  # 25

# simplify
expr = parser.parse('x * (y * atan(1))').simplify({'y': 4})
expr.toString()  # x*3.141592
expr.evaluate({'x': 2})  # 6.283185307179586

# get variables
expr = parser.parse('x * (y * atan(1))')
expr.variables()  # ['x', 'y']
expr.simplify({'y': 4}).variables()  # ['x']

Available operations

parser = Parser()
parser.parse('2 + 3').evaluate({})  # 5.0
parser.parse('2 - 3').evaluate({})  # -1.0
parser.parse('2 * 3').evaluate({})  # 6.0
parser.parse('2 / 3').evaluate({})  # 0.6666666666666666
parser.parse('2 % 3').evaluate({})  # 2.0
parser.parse('-2').evaluate({})  # -2.0
parser.parse('abs(-2)').evaluate({}) # 2.0

parser.parse('ceil(1.4)').evaluate({})  # 2.0
parser.parse('floor(1.4)').evaluate({})  # 1.0
parser.parse('round(1.4)').evaluate({})  # 1.0

parser.parse('2^3').evaluate({})  # 8.0
parser.parse('sqrt(16)').evaluate({}) # 4.0

parser.parse('sin(3.14)').evaluate({})  # 0.0015926529164868282
parser.parse('cos(3.14)').evaluate({})  # -0.9999987317275395
parser.parse('tan(3.14)').evaluate({})  # -0.0015926549364072232

parser.parse('asin(1)').evaluate({})  # 1.5707963267948966
parser.parse('acos(1)').evaluate({})  # 0.0
parser.parse('atan(1)').evaluate({})  # 0.7853981633974483

parser.parse('log(2.7)').evaluate({})  # 0.9932517730102834
parser.parse('exp(1)').evaluate({})  # 2.718281828459045

parser.parse('log(E)').evaluate({})  # 1.0
parser.parse('cos(PI)').evaluate({})  # -1.0

parser.parse('x||y').evaluate({'x': 2, 'y': 3})  # '23'