Mac Port install arguments
You need to reinstall root from macports and tell it what variants (i.e. additions it needs)

port info root lists the variants e.g.


  avahi, clang31, clang32, clang33, cocoa, debug, fftw3, fitsio, gcc43, gcc44, gcc45, gcc46, gcc47, [+]gcc48,
                        gcc49, [+]graphviz, [+]gsl, ldap, mariadb, [+]minuit2, mysql, mysql51, mysql55, odbc, [+]opengl, percona,
                        postgresql90, postgresql92, pythia, python26, python27, python31, python32, python33, python34, qt_mac,
                        [+]roofit, ruby, [+]soversion, sqlite3, [+]ssl, [+]tmva, [+]xml, xrootd


The ones with [+] are installed by default.

So in your case choose the python version you want (e.g. python 3.3 as latest released one), also anything else you need as they are done all at the same time, so I might add qt_mac and sqlite3 as well

sudo port install root +python33 +sqlite3 +qt_mac


Note that python executable will be /opt/local/bin/python3.3 but you can use the select port to make it the one that /opt/local/bin/python uses