A thread on python-ideas is talking about the prefixes of string literals, and the regex used in IDLE. Line 25 of Lib\idlelib\colorizer.py is: stringprefix = r"(?i:\br|u|f|fr|rf|b|br|rb)?" which looks slightly wrong to me. The \b will apply only to the first choice. Shouldn't it be more like: stringprefix = r"(?:\b(?i:r|u|f|fr|rf|b|br|rb))?" ?