Post #211

http://www.debian.org/doc/packaging-manuals/python-policy/ch-python.html At any given time, the binary #package python3 will represent the current default #Debian Python 3 version; the binary package python will represent the current default Debian Python 2 version. As far as is reasonable, Python 3 and Python 2 should be treated as separate runtime systems with minimal interdependencies.