I migrated a large codebase with 2to3 and six. It took me half a day. 2to3 did roughly 60-75% of the work and six cleaned up almost all of the rest. It's not fo

I migrated a large codebase with 2to3 and six. It took me half a day. 2to3 did roughly 60-75% of the work and six cleaned up almost all of the rest. It's not foolproof, but it is surely better than nothing. It's perhaps also worth noting that I did this in late 2017. Your experience likely varies depending on when you attempted it.