fizz_buzz_with_iterators.py

"""
Example using Python's itertools and generators to implement the classic FizzBuzz problem using pythonic iterators.


Output looks like this:

	$ python fizz_buzz_with_iterator.py
	1
	2
	Fizz
	4
	Buzz
	Fizz
	7
	8
	Fizz
	Buzz
	11
	Fizz
	13
	14
	FizzBuzz
	16
	17
	Fizz
	19
	Buzz
"""

from itertools import cycle, chain, izip, islice, count

def make_cycle(n, word):
	"""returns an infinite iterator which returns the given word every n-th time and an empty string every other time:

	make_cycle(3, 'test') -> 'test', '', '', 'test', '', '', ...
	"""
	return cycle( chain([word], ['']*(n-1)) )


def concat_or_index(*iterators):
	"""returns an iterator that loops through all the provided iterators
	simultaneously and returns the concatination of all their values... unless
	the concatination is considered False, in which case it returns the index
	instead.
	"""

	for row in izip(count(), *iterators):
		index = row[0]
		result = ''.join(row[1:])
		yield result or index

if __name__ == '__main__':
	# demo of the functionality using the classic 3/5 FizzBuzz Problem
	endless_fizz_buzz = concat_or_index(make_cycle(3, 'Fizz'), make_cycle(5, 'Buzz'))

	# note that we have to skip the 0th element because the classic problem specifies
	# output starting from the 
	for result in islice(endless_fizz_buzz, 1, 21):
		print result