http://learnpythonthehardway.org/book/ex6.html
Zed seems to use %r and %s interchangeably here, is there any difference between the two? Wh
They are called string formatting operations.
The difference between %s and %r is that %s uses the str function and %r uses the repr function. You can read about the differences between str and repr in this answer, but for built-in types, the biggest difference in practice is that repr for strings includes quotes and all special characters are escaped.