making a "concordance" module—the wrong way to do it

wrong_concordance.py

concordance = dict()

def tokenize(line):
  return line.split(" ")

def feed(line):
	words = tokenize(line)
	for word in words:
		if word not in concordance:
			concordance[word] = 0
		concordance[word] += 1

def count_for_word(word):
	if word in concordance:
		return concordance[word]
	else:
		return 0

def unique_words():
	return concordance.keys()

if __name__ == '__main__':
	import sys
	check_word = sys.argv[1]
	for line in sys.stdin:
		line = line.strip()
		feed(line)
	print "count for " + check_word + ": " + str(count_for_word(check_word))
	print "unique words: " + str(len(unique_words()))