Since you mention 2.7.1, presumably you are using the Apple-suppled Python 2.7.1 in OS X.  That Python is not linked with GNU readline, rather the BSD libedit library.  As a workaround you could try installing the third-party readline package from PyPI which replaces the Python redline module with one that is statically linked with GNU readline (see  http://pypi.python.org/pypi/readline).  On the other hand, if there are more differences in behavior between Python readline linked with GNU readline and with BSD libedit, they should be documented.