def get_key_words(num_topics):
	"""asks the use for a set of key words for each topic, returns a list of list, where list i
	is the set of key words for topic i."""

	#generate list
	kw_per_topic = []

	#get key words for each topic from user
	for i in range(0, num_topics):
		kw_raw = input("Enter keywords for topic %d, seperated by space: " % (i))
		kw = kw_raw.split()
		kw_per_topic.append(kw)



	return kw_per_topic