gistfile1.py

#!/usr/bin/python
# -*- coding: utf-8 -*-

import unittest


class TestCombination(unittest.TestCase):
    ''' to check combi function '''
    def setUp(self):
        pass

    def testcombi(self):
        self.assertEqual(combi(2, 0), 1)
        self.assertEqual(combi(3, 1), 3)
        self.assertEqual(combi(4, 2), 6)
        self.assertEqual(combi(5, 3), 10)
        self.assertEqual(combi(6, 4), 15)


def combi(n, r):
    if n < 0 or r < 0:
        return False
    if n == 0 or r == 0:
        return 1
    if n == r:
        return 1
    return ((n - r + 1) * combi(n, r - 1)) / r


def main():
    unittest.main()

if __name__ == '__main__':
    main()