This notebook was prepared by Donne Martin. Source and license info is on GitHub.

Challenge Notebook

Problem: Determine if a number is a power of two.


  • Is the input number an int?
    • Yes
  • Can we assume the inputs are valid?
    • No
  • Is the output a boolean?
    • Yes
  • Can we assume this fits memory?
    • Yes

Test Cases

  • None -> TypeError
  • 0 -> False
  • 1 -> True
  • 2 -> True
  • 15 -> False
  • 16 -> True


Refer to the Solution Notebook. If you are stuck and need a hint, the solution notebook's algorithm discussion might be a good place to start.


In [ ]:
class Solution(object):

    def is_power_of_two(self, val):
        # TODO: Implement me

Unit Test

The following unit test is expected to fail until you solve the challenge.

In [ ]:
# %load
import unittest

class TestSolution(unittest.TestCase):

    def test_is_power_of_two(self):
        solution = Solution()
        self.assertRaises(TypeError, solution.is_power_of_two, None)
        self.assertEqual(solution.is_power_of_two(0), False)
        self.assertEqual(solution.is_power_of_two(1), True)
        self.assertEqual(solution.is_power_of_two(2), True)
        self.assertEqual(solution.is_power_of_two(15), False)
        self.assertEqual(solution.is_power_of_two(16), True)
        print('Success: test_is_power_of_two')

def main():
    test = TestSolution()

if __name__ == '__main__':

Solution Notebook

Review the Solution Notebook for a discussion on algorithms and code solutions.