I installed Macports on OS X Mavericks and then I switched to Homebrew. Now I upgraded to OS X Yosemite and suddenly remembered to uninstall macports so that home-brew doesn't have any build problems. But when I try to uninstall I get a platform mismatch error which is obvious as I upgraded my OS X. As I am very new at this, can anyone help with step by step instructions to completely remove macports from system.
sudo port -v -f uninstall active will not work while you haven't upgraded your MacPorts installation. You can use the MacPorts installer for Yosemite from the website to get a working MacPorts again. Once you did that, follow the official uninstall instructions.