r\'\\\' in Python does not work as expected. Instead of returning a string with one character (a backslash) in it, it raises a SyntaxError. r\"\\\"
r\'\\\'
r\"\\\"
That is because in raw strings, you need a way to escape single quotes when the string is delimited by single quotes. Same with double quotes.
http://docs.python.org/reference/lexical_analysis.html#string-literals