Simple Python documentation exception [duplicate]

My code returns an exception from a documentation string, and I can't see the issue:

def printBreak(title):
    """Prints a dotted line"""
    print("------" + title + "------")

def printWords(theWords):
    """Prints the passed array with word length and word"""
    for w in theWords:
        print(len(w), w)
    print("")

def sortWordsByLength(theWords):
    """Word array sorted by length"""
    for w in theWords:
        for i in range(len(wordsSortedByLength)):
            if len(w) > len(wordsSortedByLength[i]):
                wordsSortedByLength.insert(i,w)
                break
        else:
            wordsSortedByLength.append(w)


def main():
    printBreak("Initial word array")
    printWords(words)
    printBreak(sortWordsByLength.__doc__)
    sortWordsByLength(words[1:])
    printWords(wordsSortedByLength)

# Sort some strings
words = ['happy', 'cat', 'window', 'appetite', 'gophery', 'it', 'perky']
wordsSortedByLength = [words[0]]
main()

Error:

File "/Users/bevilacm/source/Python/Scripts/sortWords.py", line 7
for w in theWords:
                 ^
IndentationError: unindent does not match any outer indentation level
[Finished in 0.1s with exit code 1]

If the documentation string is commented out in the printWords function documentation string, the code works. I expect it is something simple yet I don't see it.

Thanks!