Counter the Number of words in an arbitrary strings

word_counter.py

sentence = " this is a  debug message"

def counter(str):
	"this should be done with no standard library"
    words = 0
    prevSpace = True
    indx = 0
    for i in sentence:
        if str[indx] != " " and prevSpace:
            words += 1
        prevSpace = str[indx] == " "
        indx += 1
    return words

# test cases
sentence1 = " this is a  debug message"
sentence2 = "this is    a  debug   message"
print(counter(sentence1))
print(counter(sentence2))