homework

calc.py

#!/usr/bin/env python3
import re
import math


class CalculationException(Exception):
    pass


class Calculation:
    def __init__(self, string):
        self.string = self._parse(string)

    def _parse(self, string):
        return ''.join([i for i in string if i != ' '])

    def calculate(self):
        string = self.string
        while True:
            if string.isnumeric():
                return string

            string = self._calculate(string)

    def _calculate(self, string):
        """
        Priorities:
        1. sqrt
        2. a * b or a / b
        4. ()
        5. a + b or a - b
        """
        m = re.search('sqrt\((\d+)\)', string)
        if m:
            return string.replace( 'sqrt(%s)' % m.groups()[0], '%s' % int(math.sqrt(int(m.groups()[0]))) )

        m = re.search('(\d+)\*(\d+)', string)
        if m:
            l, r = m.groups()[0], m.groups()[1]
            return string.replace( '%s*%s' % (l, r), '%s' % int( (int(l) * int(r) ) ) )

        m = re.search('(\d+)\/(\d+)', string)
        if m:
            l, r = m.groups()[0], m.groups()[1]
            return string.replace( '%s/%s' % (l, r), '%s' % int( int(l) / int(r) ) )

        m = re.search('\((\d+)\)', string)
        if m:
            return string.replace('(%s)' % (m.groups()[0]), '%s' % (m.groups()[0]))

        m = re.search('\((\d+)\+(\d+)\)', string)
        if m:
            l, r = m.groups()[0], m.groups()[1]
            return string.replace('%s+%s' % (l, r), '%s' % (int(l) + int(r)))

        m = re.search('\((\d+)\-(\d+)\)', string)
        if m:
            l, r = m.groups()[0], m.groups()[1]
            return string.replace('%s-%s' % (l, r), '%s' % (int(l) - int(r)))

        m = re.search('(\d+)\+(\d+)', string)
        if m:
            l, r = m.groups()[0], m.groups()[1]
            return string.replace('%s+%s' % (l, r), '%s' % (int(l) + int(r)))

        m = re.search('(\d+)\-(\d+)', string)
        if m:
            l, r = m.groups()[0], m.groups()[1]
            return string.replace('%s-%s' % (l, r), '%s' % (int(l) - int(r)))

        raise CalculationException('Wrong formula!')


if __name__ == '__main__':
    calc = Calculation('( 2 + ( ( 4 + 6 ) * sqrt(9)) / 2 )')
    print(calc.calculate())

    calc = Calculation('( 2 + ( ( 4 + 6 ) * (9 * 2) - ( 5 - 1)))')
    print(calc.calculate())

calc_tests.py

#!/usr/bin/env python3
import unittest
from calc import Calculation
from calc import CalculationException


class CalculationTests(unittest.TestCase):
    def test_plus(self):
        calc = Calculation('5 + 3')
        self.assertEqual(calc.calculate(), '8')

    def test_minus(self):
        calc = Calculation('6 - 4')
        self.assertEqual(calc.calculate(), '2')

    def test_times(self):
        calc = Calculation('2 * 4')
        self.assertEqual(calc.calculate(), '8')

    def test_divide(self):
        calc = Calculation('6 / 3')
        self.assertEqual(calc.calculate(), '2')

    def test_brackets(self):
        calc = Calculation('5 * (2 + 3)')
        self.assertEqual(calc.calculate(), '25')

    def test_together(self):
        calc = Calculation('( 2 + ( ( 4 + 6 ) * sqrt(9)) / 2 )')
        self.assertEqual(calc.calculate(), '17')

    def test_nagative(self):
        with self.assertRaises(CalculationException):
            calc = Calculation('( 2 + ( ( 4 + 6 ) * st(9)) / 2 )')
            calc.calculate()


if __name__ == '__main__':
    unittest.main()