You're both half-right: the "standard" App Engine environment is "Python 2.7 onl...

elithrar on May 7, 2017 | parent | context | favorite | on: Key differences between Python 2.7.x and Python 3....

You're both half-right: the "standard" App Engine environment is "Python 2.7 only", via the link you just gave. The newer, flexible env (with less bullt-ins) does 3.x too.