fizz_buzz.py

#!/usr/bin/env python
#
# License: BSD
# Copyright: Adam Allevato 2018
#
# FizzBuzz example program and associated tests.
#

from cStringIO import StringIO
import sys


def main():
    fizz_buzz()


class Capturing(list):
    """
    Captures command line output into a variable. Used for unit tests. See:
    https://stackoverflow.com/questions/16571150/how-to-capture-stdout-output-from-a-python-function-call
    """
    def __enter__(self):
        self._stdout = sys.stdout
        sys.stdout = self._stringio = StringIO()
        return self
    def __exit__(self, *args):
        self.extend(self._stringio.getvalue().splitlines())
        del self._stringio    # free up some memory
        sys.stdout = self._stdout

def fizz_buzz():
    """
    Print the numbers 1-100, but with multiples of 3 replaced by
    "Fizz" and multiples of 5 replaced by "Buzz".
    """
    for idx in range(100):
        s = ""
        i = idx + 1
        if i % 3 == 0:
            s += "Fizz"
        if i % 5 == 0:
            s += "Buzz"
        # if the string is empty, not divisible by 3 or 5,
        # so print the number itself.
        if s == "":
            s += str(i)
        print(s)

def test():
    """
    FizzBuzz unit tests.
    """
    print("="*30)
    print("running tests...")
    with Capturing() as out:
        fizz_buzz()
    # note off-by one indices
    assert(out[2] == "Fizz")  # 3
    assert(out[98] == "Fizz")  # 99
    assert(out[0] == "1")  # etc.
    assert(out[4] == "Buzz")
    assert(out[14] == "FizzBuzz")
    assert(out[99] == "Buzz")
    assert(out[22] == "23")
    print("all tests passed.")
    print("="*30)


if __name__ == "__main__":
    test()
    print("press enter to run program")
    _ = raw_input()
    main()