http://bugs.python.org/review/15606/diff/5718/Doc/library/re.rst File Doc/library/re.rst (right): http://bugs.python.org/review/15606/diff/5718/Doc/library/re.rst#newcode540 Doc/library/re.rst:540: extension construct (so, for example, ``(?P<a_or_b> a | b)`` is a Reading this it seems to me that ``( ?:`` is allowed. Maybe saying something like "within tokens like ``(?:`` or ``(?P<...>``" is better. http://bugs.python.org/review/15606/diff/5718/Doc/library/re.rst#newcode546 Doc/library/re.rst:546: the leftmost such ``'#'`` through the end of the line are ignored. I find this paragraph a bit confusing, and would rephrase it to something like: """ All the text after and including the ``'#'`` character is considered as comment and ignored, unless the ``'#'`` is in a character class or it's preceded by an unescaped backslash. """ http://bugs.python.org/review/15606/