PYthon 3.4 question mark in text file

I have a problem: I am using Python 3.4. My code:

# -*- coding: utf-8 -*-

f = open('D:/TMP/Test.txt', 'w')
str = "Why ist there no question mark ??? "
f.write(str +'n')
f.close()

Very simple, but the result is:

Why ist there no question mark

Thanks for your help...

Best regards Geosucher