Some time ago we migrated a few hundred thousands lines of Py2 spread over dozens of services. Easiest case possible: every service can be converted and tested

Some time ago we migrated a few hundred thousands lines of Py2 spread over dozens of services. Easiest case possible: every service can be converted and tested separately. Took a calendar year of ca-a-a-arefully migrating these one by one, all while delivering stuff and making sure nothing falls apart along the way. Not pleasant. Can't recommend.