Count words in a string

def count_words(s):
        nb_words = 0
        in_word = 0
        i = 0
        while s[i] <> 0:
                if s[i] <> ' ':
                        if in_word:
                                i++
                        else:
                                nb_words++
                                in_word = 1
                else:
                        in_word = 0
                        i++