Complete the method so that it formats the words into a single comma separated value. The last word should be separated by the word 'and' instead of a comma. The method takes in an array of strings and returns a single formatted string. Empty string values should be ignored. Empty arrays or null/nil values being passed into the method should result in an empty string being returned. 

```Python
format_words(['ninja', 'samurai', 'ronin']) # should return "ninja, samurai and ronin"
format_words(['ninja', '', 'ronin']) # should return "ninja and ronin"
format_words([]) # should return ""
```
```Haskell
formatWords ["ninja", "samurai", "ronin"] -- should return "ninja, samurai and ronin"
formatWords ["ninja", "", "ronin"] -- should return "ninja and ronin"
formatWords [] -- should return ""
```

Difficulty: EASY
Starter code: def format_words(words):
	

Solutions:
def format_words(words):
	return ', '.join((word for word in words if word))[::-1].replace(',', 'dna ', 1)[::-1] if words else ''


def format_words(words):
	if not words:
		return ''
	words = [word for word in words if word]
	number_of_words = len(words)
	if number_of_words <= 2:
		joiner = ' and ' if number_of_words == 2 else ''
		return joiner.join(words)
	return ', '.join(words[:-1]) + ' and ' + words[-1]


def format_words(words):
	words = [w for w in words if w] if words else ''
	if not words:
		return ''
	return '{seq} and {last}'.format(seq=', '.join(words[:-1]), last=words[-1]) if len(words) != 1 else '{0}'.format(words[0])


def format_words(words):
	return ' and '.join(', '.join(filter(bool, words or [])).rsplit(', ', 1))


from itertools import chain

def format_words(words):
	if not words:
		return ''
	filtered = [s for s in words if s]
	nCommas = len(filtered) - 2
	nAnd = min(1, len(filtered) - 1)
	chunks = [', '] * nCommas + [' and '] * nAnd + ['']
	return ''.join(chain(*zip(filtered, chunks)))


def format_words(words):
	if not words or words == ['']:
		return ''
	words = [i for i in words if i != '']
	if len(words) == 1:
		return words[0]
	return ', '.join(words[:-1]) + ' and ' + words[-1]


def format_words(w=None):
	return ', '.join(filter(lambda _: bool(_), w))[::-1].replace(',', 'dna ', 1)[::-1] if w else ''


def format_words(words):
	if words != [''] and words != [] and (words is not None):
		l = [word for word in words if word != '']
		return ', '.join(l[:-1]) + ' and ' + l[-1:][0] if len(l) > 1 else l[0]
	return ''


def format_words(words):
	words = [w for w in words if w] if words else ''
	if not words:
		return ''
	return f"{', '.join(words[:-1])} and {words[-1]}" if len(words) != 1 else words[-1]